CN105041288A - A method of acid fracturing for fracture diversion in carbonate oil and gas reservoirs - Google Patents

Abstract

The invention provides a carbonate oil and gas reservoir fracture steering acid fracturing method, which comprises the following steps: the method comprises the following steps: injecting 50-500 cubic meters of fracturing fluid into the stratum at a discharge capacity of 2.0-15.0 cubic meters per minute; step two: injecting 5-100 cubic meters of material liquid into the stratum at a discharge capacity of 1.0-15.0 cubic meters per minute, and pumping at a discharge capacity of 0.5-5.0 cubic meters per minute when the material liquid enters a bridge blockage position in a preset seam; step three: injecting 50-500 cubic meters of fracturing fluid into the stratum at a discharge capacity of 3.0-15.0 cubic meters per minute to forcibly divert the fracture; step four: injecting acid liquor for acid etching reconstruction, wherein the injection amount is 20-300 cubic meters, and the injection speed is 2.0-15.0 cubic meters per minute; and performing the operations of the second step to the fourth step at least once. The invention provides a carbonate oil and gas reservoir fracture steering acid fracturing method, which can form a plurality of steering acid fracturing fractures after repeated temporary plugging and fracture forming, and has the advantages of temporary plugging material degradation after the acid fracturing construction is finished, small pollution to a reservoir stratum and capability of improving the acid fracturing efficiency.

Description

A method of acid fracturing for fracture diversion in carbonate oil and gas reservoirs

technical field

The invention belongs to the technical field of petroleum and natural gas exploitation, and in particular relates to a fracture diverting acid fracturing method of a carbonate rock oil and gas reservoir.

Background technique

Carbonate oil and gas reservoirs are widely distributed in my country. Carbonate reservoirs generally have natural fractures and caves, strong heterogeneity, and poor matrix physical properties. Since the current geophysical prospecting methods cannot accurately determine the specific locations of fractures and caves, drilling It is impossible to ensure that natural fractures and karst cave systems are directly put into production, and the natural production rate is low, and most of them need reservoir reconstruction before they can be put into production.

For fracture-cavity reservoirs, the main purpose of acid fracturing is to connect fractures and caves. Only when acid fracturing fractures communicate with the fracture-cavity system can acid fracturing achieve the desired effect. Acid fracturing fractures are controlled by natural fractures and stress. When the stress and the orientation of natural fractures are poorly matched with the reservoir azimuth, the wellbore is close to the reservoir and cannot communicate with the reservoir. When the stress orientation, natural fracture orientation and reservoir orientation are poorly matched, the acid fracturing fractures are controlled by the stress and natural fracture development, and the acid fracturing cannot communicate with the fracture-cavity system. The conventional method is to open windows and sidetrack. For carbonate gas reservoirs with a size of 1.5 meters, sidetracking through windows is risky, time-consuming and expensive.

Contents of the invention

In order to solve the above problems, the object of the present invention is to provide a method for acid fracturing of fractures in carbonate oil and gas reservoirs, which is a method that can improve the efficiency of acid fracturing.

In order to achieve the above object, the present invention provides a method for turning fractures in carbonate reservoirs to acid fracturing, the method comprising the following steps:

Step 1: Inject 50-500 cubic meters of fracturing fluid into the formation at a displacement of 2.0-15.0 cubic meters per minute;

Step 2: Inject the material solution into the formation at a displacement of 1.0-15.0 cubic meters per minute. When the material solution enters the bridging place in the preset fracture, pump it at a displacement of 0.5-5.0 cubic meters per minute. The total amount of the material solution The dosage is 5-100 cubic meters;

Step 3: Inject 50-500 cubic meters of fracturing fluid into the formation at a displacement of 3.0-15.0 cubic meters per minute to force the fractures to divert;

Step 4: Inject acid solution for acid etching transformation, the injection volume is 20-300 cubic meters, and the injection rate is 2.0-15.0 cubic meters/minute;

Step 5: Repeat steps 2 to 4 at least once;

Step 6: Use at least one construction string volume of displacement fluid for displacement.

The operation from step 2 to step 4 can be repeated according to the actual situation until the storage body is communicated.

After the construction is completed, the temporary plugging material is dissolved or degraded to realize the production of fractures.

In the above method, step 4 can be performed several times as required.

In the above method, preferably, the material liquid includes temporary plugging material and carrier liquid, and the weight ratio of the two is 1-10:100.

In the above method, preferably, the temporary plugging material is a soluble or degradable temporary plugging material under reservoir conditions, more preferably a water-soluble temporary plugging material, an oil-soluble temporary plugging material, a temperature-degradable temporary plugging material or a biological Degrade temporary plugging materials. Further preferably, the degree of dissolvability or degradability of the temporary plugging material is 95%-100%; more preferably, the temporary plugging material includes petroleum engineering fiber FCL, new diverting agent DCF-1 for fracturing, flexible diverting agent SR -3 or diverting agent DCF-2 for fracturing, the above products are all produced by Beijing Kemax Oilfield Chemical Agent Technology Co., Ltd. After conventional processing, the above products can be made into fibrous, granular or flake temporary plugging materials, and temporary plugging materials of different shapes can be used in combination.

In the preferred embodiment provided by the present invention, the temporary plugging material is thermally degradable temporary plugging material DCF-1. After the construction is completed, the temperature of the underground liquid gradually rises to the formation temperature, and the temporary plugging material automatically cools down at the formation temperature. degradation.

In the above method, making the material liquid enter the bridging place in the preset fracture can be realized specifically by calculating the injection volume, which is a conventional method in the art.

In the above method, preferably, the injection of the material liquid is divided into two stages. After the material liquid enters the bridging place in the preset fracture, the material liquid is injected at a lower displacement, which is beneficial to the fluid loss into the formation as soon as possible. A dense filter cake is formed at the bridge plug.

In the above method, preferably, the shape of the temporary plugging material is granular, flake or fibrous; combination of species;

By weight, when granular temporary plugging materials and fibrous temporary plugging materials are used in combination, the dosage ratio of granular temporary plugging materials to fibrous temporary plugging materials is (0.3-0.7): (0.7-0.3); When the temporary plugging material and the fibrous temporary plugging material are used in combination, the dosage ratio of the flake temporary plugging material to the fibrous temporary plugging material is (0.2-0.8): (0.8-0.2); when the granular temporary plugging material and the flake temporary plugging material When the plugging materials are used in combination, the dosage ratio of the granular temporary plugging material and the flake temporary plugging material is (0.4-0.6): (0.4-0.6); when the granular temporary plugging material, the flake temporary plugging material and the fibrous temporary plugging When materials are used in combination, the dosage ratio of granular temporary plugging material, flake temporary plugging material and fibrous temporary plugging material is (0.1-0.5):(0.2-0.4):(0.7-0.1).

In the above method, the selection of material properties is mainly determined according to the formation depth of the fracturing or acid fracturing well and the fracture pressure of the formation;

Preferably, the performance index of the granular temporary plugging material is: a particle size of 1-3 mm, a true density of 1.10-1.35 g/cm3, and a temperature resistance range of 20-200 degrees Celsius; the performance index of the sheet-shaped temporary plugging material It is: 0.1-3 mm thick, 5-10 mm round and/or similar round flakes, real density 1.10-1.35 g/cm3, temperature range 20-200 degrees Celsius; the fibrous temporary plugging material The performance indicators are: fiber diameter 10-20 microns, length 4-8 mm, real density 1.10-1.35 g/cm3, temperature range 20-200 degrees Celsius.

The performance selection of temporary plugging materials is mainly determined according to the formation depth of acid fracturing wells and the fracture pressure of formations; through the selection of temporary plugging materials with different shapes and different properties, it is beneficial to adapt to the temporary plugging of fractures with different widths and improve the temporary plugging effect. For specific reservoirs, after selecting suitable particles and fibers for mixing, the filter cake formed by temporary plugging can be made denser and the ability to plug fractures can be enhanced.

In the above method, the carrier liquid in the material liquid is a liquid with a certain viscosity under ground conditions to satisfy the suspension and carrying of the temporary plugging material. After the carrier liquid enters the fracture of the reservoir, the viscosity of the liquid decreases and the carrying capacity decreases. Gather somewhere in the crack to form a bridge plug.

In the above method, preferably, the carrier fluid is one or more of low-viscosity guar gum solution, VES fluid (viscoelastic surfactant fracturing fluid) or gelled acid fluid.

In the above method, preferably, in parts by weight, the low-viscosity guar gum solution includes the following components: 100 parts of fresh water, 0.2-0.5 parts of guar gum or super guar gum, 2-10 parts of potassium chloride, 0.03- 0.06 part of sodium hydroxide, 0.08-0.15 part of sodium carbonate, 0.08-0.12 part of sodium bicarbonate, 0.08-0.12 part of formaldehyde, 0.5-1 part of demulsifier, 0.5-1 part of high-efficiency drainage aid; wherein, the demulsifier is Condensate of alkylphenol and ethylene oxide and/or cationic surfactant, the high-efficiency drainage aid is a fluorine-containing surfactant; more preferably, the described demulsifier and efficient drainage aid are Beijing Kemax FRZ-4 demulsifier and HSC-25 high-efficiency drainage aid produced by Oilfield Chemical Technology Co., Ltd.

In the above method, preferably, in parts by weight, the VES liquid includes the following components: 100 parts of fresh water, 1-5 parts of VES-50A (produced by Beijing Kemashi Oilfield Chemical Technology Co., Ltd.), 0.5- 2 copies of VES-50B (produced by Beijing Kemax Oilfield Chemical Technology Co., Ltd.).

In the above method, preferably, in parts by weight, the gelled acid solution includes the following components: 100 parts of basic acid solution, 0.3-1.0 parts of acid solution gelling agent, 13 parts of high temperature acid solution corrosion inhibitor, 0.5 parts -1 part of demulsifier, 0.5-1 part of iron ion stabilizer, 0.5-1 part of high-efficiency drainage aid; wherein, the acid gelling agent is an acid-resistant cationic polymer, and the high-temperature acid corrosion inhibitor is aldehyde and ketone Amine condensate, the demulsifier is the condensation product of alkylphenol and ethylene oxide and/or cationic surfactant, the iron ion stabilizer is sodium ascorbate, and the high-efficiency drainage aid is fluorine-containing surface active agent; further preferably, the demulsifier, high-efficiency drainage aid, acid gelling agent, and high-temperature corrosion inhibitor are respectively FRZ-4 demulsifier and HSC-25 high-efficiency demulsifier produced by Beijing Kemax Oilfield Chemical Technology Co., Ltd. Drainage aid, KMS-50 gel, KMS-6 corrosion inhibitor.

The above-mentioned gel acid solution can also be used as the acid solution in the acid fracturing process for acid etching reformation of the reservoir.

In the above method, preferably, the acid solution is gelled acid solution, temperature-controlled viscous acid, ground crosslinking acid, DCA turning acid (cleaning turning acid), alcohol ether acid, emulsified acid, foam acid or organic soil One or several kinds of acids;

In the above method, preferably, the fracturing fluid is guar gum fracturing fluid, synthetic polymer polymeric fracturing fluid, emulsified fracturing fluid, foam fracturing fluid, clean fracturing fluid, organic fracturing fluid one or several.

In the above method, preferably, in parts by weight, the guar gum fracturing fluid or super guar gum fracturing fluid comprises the following components: 100 parts of water, 0.2-0.5 parts of guar gum or super guar gum, 2-10 Part potassium chloride, 0.03-0.06 part sodium hydroxide, 0.08-0.15 part sodium carbonate, 0.08-0.12 part sodium bicarbonate, 0.08-0.12 part formaldehyde, 0.008-0.015 part ammonium persulfate, 0.5-1 part demulsifier, 0.5 part -1 part of high-efficiency drainage aid and 0.1-1.2 parts of organic boron crosslinking agent; wherein, the demulsifier is a condensation product of alkylphenol and ethylene oxide and/or a cationic surfactant, and the high-efficiency drainage aid It is a fluorine-containing surfactant; further preferably, the demulsifier, high-efficiency drainage aid, and organoboron crosslinking agent are respectively FRZ-4 demulsifier and HSC-25 high-efficiency Drainage aid, YP-150 organic boron crosslinking agent.

In the above method, preferably, in parts by weight, the clean fracturing fluid comprises the following components: 100 parts of fresh water, 3-5 parts of viscoelastic surfactant; more preferably, the viscoelastic surfactant is Octadecyltrimethylammonium chloride; Further preferably, the viscoelastic surfactant is the VES-50 viscoelastic surfactant produced by Beijing Comax Oilfield Chemical Technology Co., Ltd.

In the above method, preferably, the displacement liquid is a low-viscosity neutral or alkaline liquid, the alkaline liquid can be a NaOH solution, the low-viscosity neutral liquid can be a low-concentration guar gum solution or slippery water, more preferably slippery water;

In the above method, preferably, the steps of stopping the pump and holding the pressure to measure the pressure drop are performed after the displacement is completed, and the pressure holding time is preferably 20 minutes.

In the above method, in the fourth step of the acid etching transformation process, after the acid injection is completed, the pump can be stopped for a period of time to form closed acidification and increase the diversion capacity of the seam.

In the above method, preferably, the method includes the step of injecting acid solution (which may be the acid solution used in acid etching reconstruction) before step 1 to reduce formation stress;

The acid solution is preferably alcohol ether acid, which includes the following components: 100 parts of 20% HCl, 0.3 part of gelling agent, 2 parts of corrosion inhibitor, 1 part of iron ion stabilizer and 8 parts of alcohol ether; Agent, corrosion inhibitor, iron ion stabilizer, and alcohol ether are KMS-50 gelling agent, KMS-6 corrosion inhibitor, KMS-7 iron ion stabilizer, DCA produced by Beijing Kemax Oilfield Chemical Technology Co., Ltd. -4 alcohol ether.

In the above-mentioned method, preferably, in step 4, the acid-etching reformation is to use two kinds of acid liquids for two-stage alternate injection, which is beneficial to improve the conductivity of acid-etched fractures and increase the effective length of acid-etched fractures; preferably The two-stage alternating injection method of clean steering acid + alcohol ether acid (inject the two acids several times, inject one acid first and then the other acid for the first time, and then inject each batch separately similar to the above injection method Secondary acid, this is called alternating injection); clean diversion acid does not contain polymers, has no damage to the reservoir, and becomes sticky after reacting with calcium carbonate underground, which is conducive to increasing the acid etching distance and dredging underground micro-cracks , Adding alcohol ether acid is beneficial to clean the residual acid that becomes viscous underground and quickly breaks the glue without residue and no damage to the formation.

The components of the cleaning steering acid include: 100 parts of 20% HCl, 8-12 parts of cleaning steering acid main agent, 0.15-0.35 parts of gelling agent and 1-4 parts of corrosion inhibitor; cleaning steering acid main agent, gelling agent Agents and corrosion inhibitors are DCA-1 clean steering acid main agent, KMS-50 gelling agent, and KMS-6 corrosion inhibitor produced by Beijing Kemax Oilfield Chemical Technology Co., Ltd.;

As the glycol ether acid, the aforementioned glycol ether acid for reducing formation stress can be used.

In the above method, when the previously acid fractured fractures do not show communication with fracture-cave bodies (the pressure has not dropped significantly), the material liquid is injected into the fractures that have been opened with a relatively low displacement, because the material liquid carries The fluid viscosity is low, and the fluid can leak into the formation at a faster rate. At this time, the displacement is low, and the artificial fracture width is small. Under the stress of the fracture wall, the fracture can be closed quickly (if the fluid loss rate is slow , after injecting the material liquid, stop the pump for a period of time and let the fracture close), so that the temporary plugging material can form a denser filter cake in the closed fracture, forcing the subsequent fracture-making fluid to transfer to other oil and gas intervals, resulting in new artificial crack.

In the process of switching from fractures in carbonate gas reservoirs to acid fracturing, if the first fracturing fails to communicate with the fracture-cavity system, the fractures fractured for the first time can be temporarily plugged in different places, and then new ones can be opened. Artificial cracks, such as temporary plugging at a certain part in the middle of the crack, prevent the crack from extending in the original direction, and the net pressure of the crack increases, forcing the crack to reopen at the weaker part of the crack to make the crack turn; or form a temporary crack at the crack opening. Plugging, so that fractures are opened in other directions at the wellbore.

In the above method, preferably, temporary plugging in the crevice or temporary crevice plugging can be formed by using the temporary plugging material. The temporary plugging of the seam and the temporary plugging in the seam can be adjusted by injecting the displacement of the temporary blocking diverting agent. If the displacement is low (0.5-2 cubic meters per minute), it is mainly the temporary blocking of the seam. If the displacement is high (2-5 cubic meter per minute), it is temporary blocking in the seam.

Temporary plugging materials are used to temporarily plug old fractures and at the same time force fractures to open in new directions. The opening, extension length and direction of fractures in new directions are affected by the stress field of the formation and natural fractures. The directions of the maximum and minimum principal stresses are deflected, and the fracture may turn during the turning fracturing process. Wells produced after fracturing may be affected by artificial fractures, pore thermoelastic stress, water injection/production activities in adjacent wells, and proppant embedding stress. The turning radius of hydraulic fracturing artificial fractures is also related to multiple parameters such as ground stress difference, fracturing fluid viscosity, and fracturing displacement. The smaller the difference in ground stress, the greater the viscosity of the fracturing fluid and the higher the fracturing displacement, the greater the turning radius of the fracture. In view of the above analysis, diverting fracturing should select wells that may have large in-situ stress changes around the wellbore and use appropriate technology for diverting fracturing, as shown in Figure 1.

Under homogeneous conditions, the propagation direction of artificial fractures is always perpendicular to the minimum principal stress of the current in-situ stress field. However, in heterogeneous fractured carbonate reservoirs, the propagation direction of artificial fractures is not only controlled by the orientation and size of the current in-situ stress, but also controlled by the natural fractures formed under the action of the main stress field. The final orientation of artificial fractures is complicated. In order to realize the transformation of fractures into acid fracturing during acid fracturing and provide parameter basis for design, theoretical calculations and experiments were performed to simulate the law of artificial fracture initiation and fracture extension in natural fractured rock blocks.

On wellbore walls with natural fractures, the initiation direction of artificial fractures is: when high-angle fractures develop in fractured carbonate reservoirs, since the tensile strength of natural fractures is smaller than that of rocks, natural fractures during fracturing Fractures may preferentially open and extend to form fracturing artificial fractures, so that the fracturing fractures no longer strictly extend along the direction of the maximum principal stress. Field imaging logging data also mostly reflect that acid fracturing fractures are the expansion and extension of fractures along the bottom of the well.

However, without considering the change of the stress field near the borehole wall caused by fracturing fluid seepage, the tensile strength of natural fractures, the tensile strength of rocks, the difference between the maximum and minimum horizontal principal stresses, and the gap between the fracture surface and the maximum horizontal principal stress The horns will play a leading role. In the stress state σ ₁ >σ ₂ >σ ₃ and σ ₂ is nearly upright, if the angle between the horizontal maximum principal stress σ ₁ and the normal to the fracture surface is α, then the angle between the fracture surface and the horizontal maximum principal stress β = π/2+α, the normal stress σ _n acting on the fracture surface is:

σ _n ＝(σ ₁ +σ ₃ )/2-[(σ ₁ -σ ₃ )cos2β]/2(1)

The ultimate fracture pressure for crack opening is: P _ff =σ _n +S _f –P _p (2)

The ultimate rupture pressure at which new cracks are formed along the direction of the maximum principal stress is:

P _fR ＝σ ₃ +S _R -P _p (3)

In the formula: P _p ——reservoir pore pressure, MPa;

S _R —tensile strength of rock, MPa;

S _f ——crack tensile strength, MPa;

σ ₁ , σ ₃ ——maximum and minimum horizontal principal stress, MPa.

When the construction fracture pressure P _f >P _ff or P _f >P _fR , the cracks open or the rock breaks, forming artificial cracks. Obviously, the conditions for the opening of natural fractures or the formation of new fractures along the maximum principal stress orientation depend on the relative size of P _ff and P _fR . Under certain geological conditions, if the difference between P _ff and P _fR is small (within 8MPa), it is possible to turn the fracture through certain technological measures.

In the process of fracture extension, when artificial fractures intersect with natural fractures, the orientation of artificial fractures is also similar to the situation at the wellbore wall above. Then add temporary plugging material in the fracture to increase the liquid inlet pressure of the opened fracture, and then a new fracture may be formed in another direction, and the new fracture is selected again at the next selection point (intersection point crossing the natural fracture), It is possible to form complex tortuous cracks. The orientation law of the new fracture at each selected point is affected by factors such as the angle between the artificial fracture and the natural fracture, the tensile strength of the natural fracture, and the angle between the natural fracture and the maximum horizontal principal stress orientation.

In the method provided by the present invention, the fracturing fluid can be used to create long fractures, and the reservoir body can be communicated as much as possible. If there is obvious communication sign, the remaining fracturing fluid can be used to continue to expand the communication, and finally the acid solution can be injected to reform the channel; If there are obvious signs of communication, it is necessary to use temporary plugging materials to temporarily plug the fractures to force the fractures to turn, and then continue to create fractures to try to communicate with good reservoirs in the new direction, and finally inject acid liquid to reform the channels and form natural fractures in the fracture plane. Enhances seepage and increases chances of lateral communication.

The fracture diverting acid fracturing method for carbonate oil and gas reservoirs provided by the present invention can be used for production stimulation construction of vertical wells, and can also be used for production stimulation construction of horizontal wells, inclined wells and the like.

In the above-mentioned fracture-turning acid fracturing method for carbonate oil and gas reservoirs, various agents used are prepared by mixing their respective components according to conventional methods.

During the acid fracturing process of carbonate oil and gas reservoirs, when the dominant reservoir (fracture-cavity system), wellbore, and in-situ stress direction do not match, conventional acid fracturing operations are difficult to communicate with the dominant reservoir, resulting in unsatisfactory acid fracturing effects , using the method provided by the invention can temporarily plug the fractures that have been opened or exist temporarily with the temporary plugging material, forcing artificial fractures to divert, which can increase the probability of acid fracturing fractures diverting to communicate with dominant reservoirs, and is a method that can improve the efficiency of acid fracturing method.

Description of drawings

Figure 1 is a schematic diagram of crack turning;

Fig. 2 is a graph showing the degree of degradation over time of the material solution prepared in Example 1 at 150°C;

Fig. 3 is a graph showing the change in pressure difference before and after injecting the material liquid into the micro-fractured core in Example 1.

Detailed ways

In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

Example 1

This implementation provides a method for acid fracturing of fractures in carbonate oil and gas reservoirs. The method uses material liquid to perform acid fracturing in a well A in the Halahatang Oilfield in the Tarim Basin.

1. Introduction of well conditions: Limestone reservoirs in Tarim Oilfield are widely distributed, accounting for about 40% of Tarim reserves. The reservoirs are buried deep (5000-7400 meters), with high closure pressure (greater than 80 MPa) and high temperature (120 -170°C), with strong heterogeneity, low matrix permeability (less than 0.1 mD), average porosity around 1%, and good reservoirs are all developed with large natural fractures and caves. When the orientation of the maximum principal stress is not conducive to the communication between fractured and caved bodies, the effect of conventional acid fracturing is unsatisfactory. Therefore, it is necessary to use fracture steering technology to realize multi-fracture reconstruction.

Well Ha A is Well Ha 13, which is an exploratory well in the oil-gas-rich belt of the Halaha Tang oil-gas-rich zone in the West Perimeter of the Lunnan Ordovician Buried Hill Anticline in the Tabei uplift of the Tarim Basin. The target interval of acid fracturing in this well is 6668.58-6800 meters. The seismic profile shows that the wellbore has been drilled into the beaded reflector, but no oil and gas shows have been seen in the target interval during drilling. The geophysical prospecting data shows that the fluid factor value in this well is small, and there are two high-value areas of fluid factor at 50 meters to the northwest and 96 meters to the southwest; natural fractures can be seen in the wellbore 3-8m as reflected by the far detection sound waves. The included angle between the maximum horizontal principal stress direction (NE80°±) and the natural fracture strike (NE35°) in the target layer of Well Ha A is 45°±, and the difference between the maximum horizontal principal stress and the minimum horizontal principal stress is small (mean value 3.7 MPa).

According to the geological characteristics of this well, the principle of stimulation is: use the diverted acid fracturing technology to form fractures in multiple directions as much as possible, increase the probability of communicating with possible reservoirs near the well, and perform acid etching stimulation to strive for a breakthrough. First, create fractures with a certain scale of fracturing fluid. If there is no obvious communication, use fibers to temporarily plug and force the fractures to turn, and then continue to create fractures to try to communicate with good reservoirs in the new direction; finally inject acid to reform the channels and form The reconstruction of natural fractures in the fracture plane enhances seepage capacity and increases the probability of lateral communication.

Specific plan: first use acid fluid to reduce the stress, and then use fracturing fluid to create long fractures to communicate as much as possible; if there are obvious signs of communication, continue to use fracturing fluid to continue to expand the communication, and finally carry out the second stage of clean steering acid + alcohol ether acid Alternate injection; if the pressure is high during construction and the signs of communication are not obvious, the material liquid will be squeezed low, and the cracking liquid will be forced to divert to seam making after high squeeze, and then the clean steering acid + alcohol ether acid will be alternately injected in two stages; finally, the low displacement will be replaced , forming closed acidification.

Acid fracturing string used in construction:

The string structure from top to bottom is: 3-1/2″BG110SE (δ6.45mm) tubing + 3-1/2″P110E (δ6.45mm) repair tubing + 3-1/2″ telescopic tube (telescopic distance 6m )+2-7/8″normally closed valve+7″MCHR packer+2-7/8″P110E tubing+ball catcher+2-7/8″tubing shoe.

2. The process of acid fracturing construction is as follows:

(1) Pretreat the formation with 20 cubic meters of alcohol ether acid at a displacement of 2.0-3.0 cubic meters per minute to reduce the fracture pressure of the formation;

(2) inject 170 cubic meters of fracturing fluid (jelly) into the formation at a displacement of 5.0-5.5 cubic meters per minute, and press open the formation to form artificial fractures;

(3) Pump 15 cubic meters of material liquid at a displacement of 2.0-2.5 cubic meters per minute;

(4) Use 25 cubic meters of 1.0-1.5 cubic meters per minute to continue pumping the material liquid. After the liquid is lost to the formation, and after the fracture is closed, the temporary plugging material forms a denser filter cake in the fracture;

(5) Pump 175 cubic meters of jelly into the formation at a displacement of 5.0-5.5 cubic meters per minute, force the fracture to turn, and form a hydraulic fracture in a new direction to increase the communication probability;

(6) Pump 100 cubic meters of clean diverting acid at a displacement of 5.5-6.0 cubic meters per minute to acid-etch the decompressed fractures to form high-conductivity acid-etched fractures so that the reservoir body and the wellbore are connected;

(7) Pump 50 cubic meters of alcohol ether acid at a displacement of 5.5-6.0 cubic meters per minute to acid-etch the fractures to form high-conductivity acid-etched fractures to connect the reservoir body with the wellbore;

(8) Pump 60 cubic meters of clean diverting acid at a displacement of 5.5-6.0 cubic meters per minute to acid-etch the decompressed fractures to form high-conductivity acid-etched fractures so that the reservoir body and the wellbore are connected;

(9) Pump 30 cubic meters of alcohol ether acid at a displacement of 6.0-2.0 cubic meters per minute to acid-etch the opened fractures to form high-conductivity acid-etched fractures to connect the reservoir body with the wellbore; A large amount of alcohol ether acid is injected to form closed acidification and increase the drainage capacity of the seam;

(10) Stop the pump for 10 minutes and wait for the cracks to close to form closed acidification and increase the diversion capacity at the cracks;

(11) Replace 30 cubic meters of slick water with a displacement of 1.0-2.5 cubic meters per minute;

(12) Stop the pump and hold the pressure for 10 minutes to measure the pressure drop;

(13) After the construction liquid returns to the formation temperature (about 2-3 hours), the material liquid will degrade naturally.

3. The material liquid used in this embodiment is:

The temporary plugging material (DCF-1 produced by Beijing Kemax Oilfield Chemical Technology Co., Ltd.), the temporary plugging material is made into fibrous and granular after conventional processing, and then mixed for use. Among them, the fibrous temporary plugging The mass ratio of material to granular temporary plugging material is 6:4. The mixed temporary plugging material is added to the carrier fluid to obtain a material liquid, the carrier fluid is a clean fracturing fluid, and the mass ratio of the temporary plugging material to the carrier fluid is 2:100; in parts by weight, the composition of the clean fracturing fluid Parts are: 95 parts of fresh water and 5 parts of viscoelastic surfactant (VES-50 produced by Beijing Kemax Oilfield Chemical Technology Co., Ltd.).

Fig. 2 is a graph showing the degree of degradation of the above-mentioned material solution over time at 150°C.

The pressure difference before and after injecting the material solution prepared in this example into the microfractured core was tested (see Figure 3 for details).

Select 4 split cores to simulate artificial fractures, add a certain confining pressure (10-20MPa) to the cores, and then inject the material liquid into the artificial fractures under different injection pressures (0-3MPa), and compare the material liquid before and after entering the artificial fractures pressure response;

It can be seen from Figure 3 that after the material liquid enters the artificial fracture, the pressure increases significantly, indicating that the temporary plugging effect of the fracture is better.

4. The fracturing fluid used in this example is super guar gum fracturing fluid:

In parts by weight, the components of the super guar gum fracturing fluid are: 100 parts of fresh water, 0.5 parts of super guar gum, 4 parts of potassium chloride, 0.04 parts of sodium hydroxide, 0.08 parts of sodium carbonate, 0.08 parts of sodium bicarbonate, 0.1 1 part of formaldehyde, 0.01 part of ammonium persulfate, 1 part of FRZ-4 demulsifier, 1 part of HSC-25 high-efficiency drainage aid, 0.6 part of YP-150 organoboron crosslinking agent, the last three components are Beijing Kemai Products produced by Shi Oilfield Chemical Technology Co., Ltd.

5. During the construction, use the two-stage alternate injection method of clean steering acid + alcohol ether acid:

In parts by weight, the composition of the cleaning steering acid is: 100 parts of 20% HCl, 10 parts of cleaning steering acid main agent, 0.25 parts of gelling agent and 2 parts of corrosion inhibitor. The above-mentioned cleaning and diverting acid main agent, gelling agent, and corrosion inhibitor are respectively DCA-1, KMS-50, and KMS-6 produced by Beijing Kemax Oilfield Chemical Technology Co., Ltd.

In parts by weight, the components of the alcohol ether acid are: 100 parts of 20% HCl; 0.3 parts of gelling agent, 2 parts of corrosion inhibitor, 1 part of iron ion stabilizer and 8 parts of alcohol ether. The gelling agent is KMS-50, the corrosion inhibitor is KMS-6, the iron ion stabilizer is KMS-7, and the alcohol ether is DCA-4, all produced by Beijing Kemax Oilfield Chemical Technology Co., Ltd.

6. Construction effect

During construction, when the fracturing fluid was pumped in step (2), the oil pressure showed a downward trend, reflecting the development of certain natural fractures near the well; after the pumping material fluid was in place, the oil pressure was 45.5 MPa, and the displacement was stable at 0.8 cubic meters m/min, the oil pressure rises to 48.7 MPa, an increase of 3.2 MPa, converted into a fracturing fluid with a density of 1.00 (the density of this well is 1.14 g/cubic centimeter), and the oil pressure increases by 9.2+3.2=12.4 MPa , the steering effect is obvious. In the stage of injecting the fracturing fluid in step (5), the pump pressure suddenly dropped from 91.7 MPa to 60 MPa, a decrease of 31.7 MPa, and turned to communicate with the beaded reservoir. When injecting acid, the oil pressure is low, and the acid etching effect is obvious. The pump stop pressure is 1.4 MPa, which is relatively low, indicating that the pressure has rapidly diffused into the reservoir and communicated with the reservoir.

Before acid fracturing, the well had no production. After acid fracturing using the above-mentioned method of acid fracturing in carbonate oil and gas reservoirs, a 4 mm choke was used for production. The oil pressure was 20.2 MPa, and the daily oil production was 100 cubic meters. /day, equivalent to a daily gas production of 6587 cubic meters/day.

Claims (10)

1. carbonate rock hydrocarbon reservoir crack turns to an acid fracturing method, and the method comprises the following steps:

Step one: the fracturing fluid injecting 50-500 cubic meter with the discharge capacity of 2.0-15.0 cubic meters per minute to stratum;

Step 2: with the discharge capacity of 1.0-15.0 cubic meters per minute to stratum injection material liquid, preset bridge blinding place in seam when material liquid enters, with the discharge capacity infusion of 0.5-5.0 cubic meters per minute, total consumption of material liquid is 5-100 cubic meter;

Step 3: with the discharge capacity of 3.0-15.0 cubic meters per minute, the fracturing fluid of 50-500 cubic meter is injected stratum, make crack forced steering;

Step 4: inject acid solution and carry out acid etching transformation, injection rate is 20-300 cubic meter, and injection rate is 2.0-15.0 cubic meters per minute;

Step 5: at least repetition step 2 is to the operation of step 4;

Step 6: use the displacement fluid of at least one operating tool string volume to replace.

2. the method for claim 1, wherein described material liquid comprises temporary stifled material and carries liquid, and the weight ratio of the two is 1-10: 100.

3. method as claimed in claim 2, wherein, the described material that blocks up temporarily is that solubilized or Degradable temporary block up material under reservoir conditions, and preferably water-soluble stifled material, oil-soluble temporarily block up material temporarily, temperature degrades temporary stifled material or biodegradation stifled material temporarily;

Further preferably, stifled material comprises petroleum works fiber FCL, pressure break novel steering agent DCF-1, flexible agent SR-3 or pressure break diversion agent DCF-2 temporarily, and the said goods is produced by Beijing KeMaiShi Oil Field Chemical regent Technology Co., Ltd.

4. method as claimed in claim 3, wherein, the shape of described stifled material is temporarily graininess, sheet or threadiness; Be preferably graininess stifled material, sheet stifled material and the threadiness combination of one or more temporarily in stifled material temporarily temporarily;

By weight, when graininess temporarily stifled material and threadiness stifled combination of materials apply temporarily time, it is (0.3-0.7) that graininess blocks up the amount ratio that material and threadiness block up material temporarily temporarily: (0.7-0.3);

When sheet temporarily stifled material and threadiness stifled combination of materials apply temporarily time, it is (0.2-0.8) that sheet blocks up the amount ratio that material and threadiness block up material temporarily temporarily: (0.8-0.2);

When graininess temporarily stifled material and sheet stifled combination of materials apply temporarily time, it is (0.4-0.6) that graininess blocks up the amount ratio that material and sheet block up material temporarily temporarily: (0.4-0.6);

When graininess stifled material, sheet stifled material and threadiness stifled combination of materials application temporarily temporarily temporarily, the amount ratio of graininess stifled material, sheet stifled material and threadiness stifled material temporarily temporarily is temporarily (0.1-0.5): (0.2-0.4): (0.7-0.1).

5. method as claimed in claim 4, wherein,

The performance indications that described graininess blocks up material are temporarily: particle diameter 1-3 millimeter, real density 1.10-1.35 gram/cc, temperature resistant range 20-200 degree Celsius;

The performance indications of described sheet stifled material are temporarily: the tablet of the circular and/or similar circle of thickness 0.1-3 millimeter, 5-10 millimeter, real density 1.10-1.35 gram/cc, temperature resistant range 20-200 degree Celsius;

The performance indications that described threadiness blocks up material are temporarily: fibre diameter 10-20 micron, length 4-8 millimeter, real density 1.10-1.35 gram/cc, temperature resistant range 20-200 degree Celsius.

6. method as claimed in claim 2, wherein, described in carry liquid be one or more in low viscosity melon sol solution, VES liquid or gelling acid solution;

Preferably, with parts by weight, described low viscosity melon sol solution comprises following component: 100 parts of fresh water, 0.2-0.5 part melon glue or super melon glue, 2-10 part potassium chloride, 0.03-0.06 part NaOH, 0.08-0.15 part sodium carbonate, 0.08-0.12 part sodium acid carbonate, 0.08-0.12 part formaldehyde, 0.5-1 part demulsifier, the efficient cleanup additive of 0.5-1 part;

Preferably, with parts by weight, described VES liquid comprises following component: 100 parts of fresh water, 1-5 part VES-50A, 0.5-2 part VES-50B;

Preferably, with parts by weight, described gelling acid solution comprises following component: 100 parts of basic acid solutions, 0.3-1.0 part acid liquor gellant, 13 portions of high temperature corrosion inhibitors for acidic media, 0.5-1 part demulsifier, 0.5-1 part ferrous stability, the efficient cleanup additives of 0.5-1 part; Wherein, described acid liquor gellant is antiacid cationic polymer, described high-temperature acid corrosion inhibiter is aldehyde ketone amine condensation product, described demulsifier is condensation product and/or the cationic surfactant of alkyl phenol and oxirane, described ferrous stability is sodium ascorbate, and described efficient cleanup additive is fluorine-containing surfactant; Further preferably, described demulsifier, efficient cleanup additive, acid liquor gellant, gel are FRZ-4 type demulsifier, the efficient cleanup additive of HSC-25 type, KMS-50 type acid liquor gellant, the KMS-6 type corrosion inhibiter that Beijing KeMaiShi Oil Field Chemical regent Technology Co., Ltd produces.

7. the method for claim 1, wherein said acid solution is gelling acid solution, temperature control becomes sticky acid, ground surface crosslinking acid, DCA turn in acid, alcohol ether acid, emulsified acid, foamed acid or buffer regulated HF acid one or more;

Described fracturing fluid is one or more in guar gum fracturing fluid, synthesis based high molecular polymeric fracturing fluids, Emulsified fracturing fluid, foam fracturing fluid, clean fracturing fluid, organic fracturing fluid.

8. method as claimed in claim 7, wherein,

With parts by weight, described guar gum fracturing fluid or super guar gum fracturing fluid comprise following component: 100 parts of water, 0.2-0.5 part melon glue or super melon glue, 2-10 part potassium chloride, 0.03-0.06 part NaOH, 0.08-0.15 part sodium carbonate, 0.08-0.12 part sodium acid carbonate, 0.08-0.12 part formaldehyde, 0.008-0.015 part ammonium persulfate, 0.5-1 part demulsifier, the efficient cleanup additive of 0.5-1 part and 0.1-1.2 part organic borate cross-linkers; Preferably, described demulsifier, efficient cleanup additive, organic borate cross-linker are FRZ-4 type demulsifier, the efficient cleanup additive of HSC-25 type, the YP-150 type organic borate cross-linker that Beijing KeMaiShi Oil Field Chemical regent Technology Co., Ltd produces;

Preferably, with parts by weight, described clean fracturing fluid comprises following component: 100 parts of fresh water, 3-5 part viscoelastic surfactants; Further preferably, described viscoelastic surfactant is octadecyl trimethyl ammonium chloride.

9. the method as described in claim 1 or 7, wherein, the method injects acid solution to reduce the step of reservoir stress before being included in step one;

Described acid solution is preferably alcohol ether acid, and it comprises following component: 100 parts of 20%HCl, 0.3 part of gelling agent, 2 parts of corrosion inhibiter, 1 part of ferrous stability and 8 parts of alcohol ethers; Described gelling agent, corrosion inhibiter, ferrous stability, alcohol ether are respectively KMS-50 gelling agent, KMS-6 corrosion inhibiter, KMS-7 ferrous stability, the DCA-4 alcohol ether that Beijing KeMaiShi Oil Field Chemical regent Technology Co., Ltd produces.

10. the method as described in claim 1 or 7, wherein, in step 4, described acid etching transformation is the mode that use two kinds of acid solutions carry out secondary alter least-squares; Be preferably the secondary alter least-squares mode of visco-elastic surfactant acid+alcohol ether acid;

The component of described visco-elastic surfactant acid comprises: 100 parts of 20%HCl, 8-12 part visco-elastic surfactant acid hosts, 0.15-0.35 part gelling agent and 1-4 part corrosion inhibiter; Described visco-elastic surfactant acid host, gelling agent, corrosion inhibiter are respectively DCA-1 visco-elastic surfactant acid host, KMS-50 gelling agent, the KMS-6 corrosion inhibiter that Beijing KeMaiShi Oil Field Chemical regent Technology Co., Ltd produces.