MX2011001683A - Improved composition, method for preparing and using oil-base ultralight fluids for drilling depressed zones with active lutite. - Google Patents

Abstract

The present invention refers to an improved composition, preparation and application of an oil-base ultralight drilling fluid, which is foamy with a half-life longer than 10 hours, useful for drilling depressed oil fields with the presence of active clay and crumbly bodies with temperatures higher than 180°C. The ultralight fluid is resistant to pollutants from salty water, crude oil, acid gases, cement and drilling debris. This fluid may be used for drilling, repairing and finishing wells by using the Underbalance Drill method or the Controlled Pressure Drill or the traditional drilling method using gas (nitrogen, air, amongst others). A foam generator and/or a diffuser is used in an individual or combined manner for reducing the specific gravity of the fluid to values lower than 0.2, the fluid may pumped to the well. Another embodiment of the invention is that the stability of the fluid is improved upon being subjected to the temperature effects and may be pumped to the well without problems of cavitation by means of a disc pump connected to the sludge pump suction.

Description

IMPROVED COMPOSITION, METHOD OF PREPARATION AND USE OF ULTRALIGHT BASED FLUIDS FOR THE DRILLING OF DEPRESSED ZONES WITH ACTIVE LITTLE FIELD OF THE INVENTION The present invention relates to the composition, method of preparation and application of a system of ultralight drilling fluid base oil foamed with average life times of more than 20 minutes and up to 10 hours, which can be used for drilling holes. Paleocene, Cretaceous and Jurassic formations of the depressed oil fields, and more specifically to drill in a safe way the clay bodies (active shales) that are embedded in these formations and with high thermal gradients (greater than 180 ° C).

The oil-based foamed fluid (ultralight) of this invention can be used for the drilling, repair and completion of oil wells using the method of Drilling Under Balance (UBD) or Drilling with Controlled Pressure (PD, for its Acronyms in English) or the traditional method of drilling using cryogenic nitrogen gas, membrane nitrogen, air or any other gas or mixtures thereof, in order to reduce the specific gravity of the fluid in a range of 0.8 to 0.2.

BACKGROUND OF THE INVENTION For the extraction of hydrocarbons it is necessary to drill the wells with the use of a drilling fluid using the traditional rotary drilling technique, which makes use of a drilling fluid (traditionally known as sludge) that can be water based, oil based or use a gas in order to carry out multiple functions, among which the following stand out: counteract the pressures of the drilling fluids, cool and lubricate the auger, carry the perforated cuttings to the surface for its separation and recycling of the previous fluid conditioning.

To exploit an oil field it is necessary to drill, in a programmed manner, several development wells, however, as the number of wells drilled increases, and hydrocarbons are extracted from the subsoil, reservoir pressure is reduced gradually, to the degree that the hydrocarbons no longer flow on their own to the surface, thus causing what we know in the state of the art of drilling as deposits or depressed zones. Thus, by continuing to drill more wells in the same field, there is a need to use ultralight fluids, with specific gravities of less than 0.9, since if fluids with higher density are used, problems of partial and total circulation losses may be caused. the fracture of the formation or by the presence of fissures and natural caverns, this situation of loss of circulation generates other collateral problems such as: pipe sticking, dragging, friction, packing of the string, presence of acid gases that can cause failure of the drill string, among others, in this way, for the drilling of said fields or depressed deposits, there is a need to use ultralight fluids with densities lower than 0.9 g / cc.

At present, certain types of fluids have been used that have not solved the problems of drilling in the aforementioned depressed areas, since the densities that are reached, although they are close and / or lower than 1.0, this density (specific gravity) ) does not reach the required values so as not to fracture the formation and to perforate with complete circulation. The type of fluids most commonly used to date are the following: bentonite fluid with densities of 1.02 to 1.05 g / cc, polymeric bentonitic fluid with densities of 1.02 to 1.05 g / cc, low density polymeric fluids with densities of 0.86 a 0.98 g / cc (80% diesel and 20% water), viscous bumps of bentonite mud (blind drilling) and fluids based on seawater with xanthan gum, silicates and maximum load lubricants with densities of 1.05 to 1.07 g / cc . Another problem that arises when drilling depressed areas with water-based fluids is that the formations where the depressed zones are located are mainly made up of marl shales of the Cretoso type, as well as limestones and dolomites, which often have interspersed with active shales. (montmorillonites, smectites, hectorites, illites, among others) that when drilled with a water-based fluid causes a series of operational problems, among which we can mention the hydration of the shales and their destruction, which causes that the diameter of the well reduce (caused by shale lint) or that the walls of the well become detached causing problems of string packing, friction, resistance and pipe sticking that can cause the loss of the well or the loss of the stage that is drilled .

To solve this problem has been increasing the use of drilling under balance with foamed fluids based on fresh water or seawater, which in order to solve the problem of hydration of clay bodies have been added certain inhibitory additives of hydration of shales (which are widely known in the environment), notwithstanding the above, said fluids do not consider additives to prevent the problem of the sloughing (dispersion) of the shales, causing them the problems described above of pipe sticking and / or packings of the drill string. Additionally, there are often losses of total circulation, derived from the existence of fractures and natural caverns of the formation, which means that it is no longer possible to monitor on the surface the formation that is cutting the bit, and therefore, not knowing the degree of activity exhibited by said clayey bodies can not specify the concentration of hydration inhibitors that must be added to the foamed water-based fluid.

In addition to the fluids mentioned above, and with the aim of avoiding the problems caused by the hydration and deletion that the water-based fluids cause to the active shales found in the depressed zones, it has been decided to drill these zones using the technique of perforation under balance with a fluid 100% oil base or reverse emulsion with high oil-water ratio, in which, in order to reduce the specific gravity of the sludge is injected nitrogen gas (membrane or cryogenic) or some other gas, without However, when the circulation of the system begins with the unit under balance, and also when the circulation is interrupted, large losses of mud (70 -100 m3 per event) arise due to the lack of capacity of the fluid 100% oil to retain the nitrogen gas occluded in the mud, this causes that in the drilling of these depressed areas lose up to 2000 to 3000 m3 of fluid 100% oil base or Reverse emulsion, which greatly increases drilling costs.

In this regard, there is in the state of the art the US patent application published under no. US2007 / 0129257, published June 7, 2007, which seeks to protect a drilling method comprising the steps of: 1) adding an amount of a foaming composition to a hydrocarbon base fluid to form a foamed drilling fluid, where the foaming composition is formed by a polymer, a gelling agent, a crosslinking agent and a foaming agent; 2) mixing the foaming composition with a gas to form a pre-foam; 3) pump the foam into the drill string; 4) producing the foam when the pre-foam suffers a sufficient pressure drop to form the foam and reduce the weight of the fluid column; and 5) remove the foam from the well.

According to said application, after removing the foam from the well, it is destroyed with a sufficient amount of a defoamer, a process that can be repeated up to 10 times without the addition of any additive of the foaming composition.

The foaming agent is selected from the group of silicone foaming agents, fluorinated foaming agents or combinations thereof, the gelling agent is selected from the group of phosphate esters and mixtures or combinations thereof with their crosslinking agents. which are selected from the group of di, tri or tetravalent metals. The polymer, which is soluble in the base oil, and whose main function is to increase the viscosity of the hydrocarbon base fluid can be formed by one or more polymerizable mono or diolefin units.

The base oil may be selected from the group of synthetic hydrocarbon oils, petroleum hydrocarbons, natural oils or other similar hydrocarbons or mixtures thereof.

The maximum half-life of the foamed fluid of the invention is from 2 to 20 minutes (the average life time of the foam is defined as the time it takes the foam to reduce its original liquid volume by 50%). This particularity makes the mentioned foam have limited application for the drilling of wells with the technique of perforation under balance or controlled pressure, since the half-life times that this foam presents are not sufficient for the fluid to remain stable derived from some suspension of operations due to failure of pumps, winch, among others, and whose waiting times exceed the 20 minutes of average life time considered by the fluid referred to in the patent in question, this situation causes the foam to be destroyed in the inside of the well causing problems of packings of the string and / or loss of circulation, since when the foam is destroyed the consistency decreases (viscosity) and the fluid no longer retains its suspension power causing the perforation cuttings to settle and the liquid phase to be lost to the formation more quickly by virtue of the viscosity reduction.

It is also known that the US patent application published under no. US2010 / 0000795, published January 7, 2010, which describes a new foaming oil base drilling fluid for drilling oil or gas wells and which also includes the method of manufacture and its use. The fluid in question is constituted by a base oil, a foaming agent and a polymer that includes at least one aromatic olefin monomer and at least one diene monomer. The composition generates a stable foam at temperatures up to 350 ° F (175 ° C).

This application also seeks to protect the drilling method comprising the steps of: 1) adding an amount of a foaming composition to a hydrocarbon base fluid to form a foamed drilling fluid, wherein the foaming composition is formed by a foaming agent and a sufficient amount of a stabilizing polymer to form a stable foam at temperatures of at least 350 ° F (175 ° C) 2) pump the foam into the drill string; 3) pumping an organophilic gas into the borehole or auger at a rate sufficient to produce a foamed drilling fluid that reduces the weight of the fluid column and transports the cuttings to the surface; and 4) remove the foam from the well.

According to said application, after removing the foam from the well, it is destroyed with a sufficient amount of a defoaming agent, a process that can be repeated up to 10 times without the addition of any additive of the foaming composition.

The aforesaid foaming composition is mainly composed of: 1) a foaming agent, which is selected from the group of silicone foaming agents, fluorinated oligomeric foaming agents or polymeric foaming agents or combinations thereof; 2) a hydrocarbon base fluid, which is selected from the group of synthetic hydrocarbon fluids, petroleum hydrocarbon fluids, natural hydrocarbon fluids and mixtures thereof; and 3) a polymer which comprises at least one aromatic olefin monomer and at least one diene monomer, where the former comprise styrene, -methyl styrene, α-trifluoromethyl styrene, fluorinated styrene, alkylated styrenes, vinyl pyridine and mixtures thereof. they and the seconds comprise at least butadiene, isoprene, 2,3-dimethyl butadiene, 1,3 pentadiene or mixtures thereof.

Generally, the foaming composition is added to the oil-based fluid in a range between 0.5 and 5% by weight, and has an average life time of 2 to 5 minutes. The foaming agent is added to the base oil in a concentration of 1% by weight, the viscosifying polymer is added in a range of 0.05 to 5% by weight and the antifoaming agent can be added in a concentration that can be twice the amount of foaming agent.

Thus, in order to drill the depressed areas characterized by the presence of clayey bodies of high activity (inflatable and despicable with high contents of montraorillonites, smectites, ectorites, Hitas, among others) it is necessary to use a foamed oil base fluid that be stable, with average life times of more than 20 minutes and up to 6 hours, or more, so that when drilling does not destabilize the walls of the wells, it does not interact with the formation hydrating it or causing its dispersion (rock-fluid interaction ) and that has the capacity to lodge a gas (air, membrane nitrogen, cryogenic nitrogen, among others) and retain it, forming a stable foam under the effects of pressures and background temperatures (100 to 200 ° C), and additionally, it resists contamination, among others, of congenital water flows from the formation, invasion of crude oil, perforation cuts and acid gases (C02 and H2S). The fluid must also have the characteristic that in combination with a gas such as air, nitrogen or any other gas, it must reduce its specific gravity to values of the order of 0.8 to 0.2 and additionally possess good rheological properties that allow the cleaning of the hole with In order to improve the drilling progress, suspend the cuttings in any situation of waiting times and carry the cuts to the surface for their removal. This type of fluid is precisely the foaming oil base drilling fluid object of this invention.

OBJECTIVES OF THE INVENTION An object of the present invention is to provide a foamed oil base fluid that is stable, with average life times of more than 20 minutes and up to 6 hours, or more.

Another objective of the present invention refers to that during its use in the perforation of depressed areas said foamed oil base fluid does not destabilize the walls of the wells, which does not interact with the formation hydrating or causing its dispersion and having the capacity to accommodate a gas and retain it, forming a stable foam under the effects of pressures and background temperatures of up to 200 ° C or more.

Moreover, another objective of the present invention is that said foamed oil base fluid resists contamination of congenital water flows from formation, invasion of crude oil, perforation cuttings and acid gases (C02 and H2S), among others.

Finally, another objective of the present invention refers to that said fluid must also have the characteristic that in combination with a gas must reduce its specific gravity to values of the order of 0.8 to 0.2 and additionally possess good rheological properties to allow the cleaning of the hole in order to improve drilling progress, suspend cuts in any situation of waiting times and carry the cuts to the surface for removal.

BRIEF DESCRIPTION OF THE DRAWINGS The numerous features of the invention are described with particularity in the appended claims. A better understanding of the features and advantages of the present invention will be obtained by reference to the following detailed description which describes the illustrative embodiments, in which the principles of the invention are used, and the accompanying drawings of which: Figure 1 shows a diagram of the Circulatory System for drilling under balance with an ultralight base oil foamed with nitrogen injection according to the present invention.

Figure 2 shows a diagram of the Circulatory System for drilling with an ultra-light fluid based on foamed oil and with air injection and foam diffuser in the mud dams without using the drill rig under balance.

Figure 3 shows a general scheme of the foam diffuser used to inject air into the ultra-light fluid in the work and suction dams with the purpose of reducing the specific gravity up to values of the order of 0.25.

Figure 4 shows a diagram of the Circulatory System for drilling under balance with an ultra-light fluid base foamed oil with nitrogen injection, foam generator, and air injection with foam diffuser in the mud dams.

DETAILED DESCRIPTION OF THE INVENTION The ultralight base foamed oil fluid object of the present invention is constituted mainly by only three essential ingredients, a base oil, a foaming agent and a foam stabilizer. Unlike the foamed fluids that exist in the state of the art, the fluid does not use viscosifying polymers, nor cross-chain agents to provide stability and thermal resistance to the foam.

The base oil used can be selected, without any restriction, from the group of kerosene oils, crude oil, diesel oil, oil of natural origin, mineral oil and condensates or oil derived from similar hydrocarbons combined or mixed together, a component that it represents 90 to 99% by volume of the base composition before injecting the gas to produce the foam and thus obtain the ultra-light fluid required to drill the depressed zones constituted by sands, marls, chalkous limestones, dolomites, among others, and that among other things allows to drill the formations that contain hydratable and deleznable clayey bodies.

The foaming agent is mainly constituted by a surfactant, which can be selected from the group of silicone foaming agents, fluorinated polymers of vinyl type, perfluorinated polymers of acrylic type. More specifically, the inventors have found that a foaming agent of the type of partially perfluorinated acrylic-based polymers in combination with a stabilizing agent provides thermal stability to the ultralight oil-based fluid of up to 200 ° C, with draining times of less than 5% in a time of 6 hours, which provides a foam with average life times over 6 hours. This feature makes it possible to ensure that the fluid remains stable within the hole, under the effects of pressure and temperatures of up to 200 ° C, for long periods of time, thus avoiding the classic problems of string packing and entrapment and / or loss. of circulation caused by the decrease in the consistency (lack of stability) suffered by foamed fluids that have short half-lives (less than 20 minutes). The concentration range in which the foaming agent is used is of the order of 0.5 to 5% by volume.

The stabilizing agent is used in a concentration range that varies from 5 to 50 kg / m3 of the base oil, and can be selected from the group of polxraeros derived from carboxylic acids (dimers, trimers, among others) or from the bentonite group , montmorillonite, smectite, hectorite, saponite, beidelite or stevensite treated with quaternary salts of fatty acids, which when interacting with oleophilic compounds such as diesel oil, hydrocarbons, synthetic oils, among others, provide thixotropic properties. The organophilic compounds prepared from the aforementioned clays, prior to their incorporation into the fluid object of the present invention, are treated with dispersing agents with the purpose of maximizing their yield, the most commonly used dispersants are, among others, low weight alcohols molecular, acetone and nitroalkanes containing up to 5% water. Polymers derived from carboxylic acids can be used in a range of 0.1 to 5% vol.

Preferably, the stabilizing agent can be selected from the group of ammonium bentonite derived from the hydrogenated dimethyl diol bait, ammonium bentonite derived from the hydrogenated methyl benzyl di bait, ammonium bentonite derived from the hydrogenated dimethyl benzyl di bait and mixtures thereof.

As seen in figure 1, the prepared fluid is circulated with a sludge pump (1) through a circulatory circuit and the foam is formed with the use of a foam generator (2), to pass to a unit of injection (3) in which a gas (4) is injected to form the foam, which passes through a vertical pipe (5), a drill string (6) and an auger to return through an annular space (7). ). Preferably, the gas (4) can be membrane nitrogen, cryogenic nitrogen, air, among others. With the equipment under balance, and through a booster (8), the well is suppressed and the fluid leaves the well through a rotating head (9) to be sent to a gas-mud separator ( 10), where part of the gas is separated from the foam and solids and fluid are sent to a solids control equipment (11) where the perforation cuttings are separated.

Unlike the foams known in the state of the art that were mentioned in the background chapter, the ultralight fluid object of the present invention does not require the use of defoaming agents, since when passed through the solids control equipment and degasser releases part of the gas thus increasing its density. The ultralight fluid passes through some dams of settlement, treatment and suction to be pumped back into the well, passing previously by the foam generator and injecting the amount of gas necessary to reduce the density to the required values.

A novel aspect of this invention is that the centrifugal pump (supercharger) that has been traditionally coupled to the suction of the slurry pump has been replaced by a transfer pump with "non-contact" technology (12) that bases its principle of operation in the "drag of the viscous boundary layer," since it is widely known that traditional centrifugal pumps present severe cavitation problems because the NPSH available with foamed fluids is less than the NPSH required by the pumps centrifuges. The use of the transfer pump solves these cavitation problems derived from the handling of viscous fluids with low specific gravity, since the disc pumps work with NPSH required of half and up to a third of the NPSH required by the centrifugal pumps. that allows to pump in a more efficient way the ultralight fluid base foamed oil to the suction of the mud pump so that this in turn pumps the fluid through the circulatory circuit of the drilling equipment (auger-auger-well-annular space) . This type of disc pumps to which this invention refers are mentioned in US Patents 4,949,385; US 4,768,920 and US 4,940,385.

In a second alternative embodiment of this invention is that the oil-based foaming fluid, object of this invention, can also be aerated or aerated in sludge dams (21) with a foam diffuser (22), thus reducing the specific gravity of the fluid to values from 0.9 to 0.20 or lower depending on the amount of gas that is injected. This feature, and in combination with the use of disk pumps (23), allows the ultralight foamed fluid base oil of this second mode can be pumped to the bottom of the well through a drill string (24), avoiding this the need to use the equipment under balance and / or the injection of cryogenic nitrogen or membrane nitrogen or some other gas in the mouth of the well (vertical pipe, surface pipe or drilling floor) with the purpose of reducing the specific gravity of the ultra-light fluid to the values required to drill. Later, the fluid passes through an auger, returns through the annular space (25) to a rotating head (26) and from there it is sent through a floating line (27) to a solids control device (28) , to finally pass to a settlement dam and mixing dams and a suction dam where, if required, the necessary treatment is given with the additives that make up this fluid and the necessary air or gas is injected through the diffuser of foam to maintain the required work density.

The foam diffuser of this second embodiment is illustrated in FIG. 3, where it can be seen that the foam diffuser is preferably constituted by a pipe (31) made of carbon steel type 40, 80 or 120, stainless steel, aluminum or even plastic PVC, which is closed at one end and the other is coupled to a hose (32) that feeds a variable air flow (eg 20 to 800 cubic feet per minute) in sufficient quantity to reduce the specific gravity of the ultralight fluid at the required values. Preferably, the length of the pipe may be variable, but more specifically it may be 1 to 5 m in length and the diameter is 1"(25.4 mm) to 5" (127 mm). Additionally in the preferred embodiment said pipe has a plurality of perforations (33), whose diameter and shape can be variable, preferably homogeneously distributed, with a diameter of said perforations ranging from 0.015"(0.38 mm) to 0.5" (12.7 mm). ), with a radial spacing of the perforations which can be from 0.25"(6.35 mm) to 10" (254 mm).

The ultra-light foamed oil-based fluid is characterized in that it is formulated with a base oil, a gas, a foaming agent of polymeric type and a stabilizing agent, which in combination with a foam generator allows to reduce, at the level of sludge dams, the specific gravity of the fluid at values in a range of 0.8 to 0.20.

In addition to the two methods of application mentioned above, the versatility of the system allows these to be used mixed in a third mode as illustrated in figure 4. With this third modality a significant saving of nitrogen gas will be obtained, that is to say , the ultra-light foamed oil base fluid can be foamed in the dams using a foam diffuser (41) to lower the density with air up to a certain value (0.4 for example) and then be pumped with a sludge pump (42) to a foam generator (43), assisted by a disc supercharger pump (44); to pass to an injection unit (45) in which the amount of a gas, preferably nitrogen, necessary to reduce the specific gravity to the required values is injected, the formed foam passes through a vertical tube (46), a string of drilling (47), an auger returning through an annular space. With the equipment under balance, and through a booster (48), the well is suppressed and the fluid leaves the well through a rotary head (49) to be sent to a gas-mud separator ( 50), where part of the gas is separated from the foam and solids and fluid are sent to a solids control equipment (51) where the perforation cuttings are separated. The ultralight fluid passes through some dams of settlement, treatment and suction (where the foam diffuser is kept operating) to be pumped back into the well, passing previously through the foam generator and injecting the amount of gas needed to reduce the density to the required values.

The composition of the oil-based foaming fluid is characterized by having a thermal resistance higher than 180 ° C without problems of thermal degradation, and in this way form stable foams, which are greatly improved when subjected to the effect of temperature coming to present greater half-life times and% drainage of the liquid phase less than 5% during a time of 6 hours which provides average life times greater than 10 hours.

The oil-based foaming fluid of this invention is capable of forming a stable foam in which it accepts a gas within a liquid (hydrocarbon, diesel oil, mineral oil or crude oil) thus reducing the specific gravity of the fluid to values of the order from 0.7 to 0.25 and more preferably 0.2 or lower, depending on the amount of gas that is injected and the amount of stabilizer and foaming agent. A) Yes, by reducing the specific gravity of the foamed fluid, the hydrostatic column pressure of the drilling fluid that is pumped into the well is reduced, thus managing the specific gravities within the range required to drill the depressed areas, thus avoiding the occurrence of a loss of circulation due to the fracturing of the formation and / or the occurrence of an outbreak when the fluids of the formation are adequately controlled.

The chemical nature and the synergetic effect achieved by the combination of the foaming agent-oil-stabilizer-gas allow the ultralight foamed fluid based on oil, apart from having thermal stability higher than 180 ° C, and more properly 200 ° C, of This invention resists the most common contaminations that occur when drilling the depressed areas of the formations characteristic of the Paleocene, Cretaceous and Jurassic, as well as inhibiting the hydration and deletion of the clayey bodies that are interspersed in these formations. The most common contaminations to which we refer, among others, are the following: salt water flows, acid gases such as C02 and H2S, crude oil, perforation cuts, among others.

In conclusion, the stabilizer, in combination with the foaming agent and the base oil, produce a synergistic effect that retains the gas for long periods of time. This effect of synergy is characterized in that at rest the foaming composition presents a thixotropic behavior in such a way that it builds a gelatinous structure that traps the gas bubble, preventing it from migrating towards the surface, increasing its stability and consequently increasing its life time half. In addition to the aforementioned characteristic, the foaming composition allows, when the gas is injected, to form a stable foam at temperatures above 200 ° C.

EXAMPLES OF APPLICATION The application examples are presented in tables No. 1 to No. 6 which illustrate the preparation and behavior of the ultra-light foamed oil base fluid with and without stabilizing agent, as well as the behavior increasing and reducing the concentration thereof. Additionally, tests of thermal stability, rheological behavior and liquid phase drainage are presented when subjected to different temperatures and the action of the most common pollutants found when drilling the depressed zone.

Table No. 1 .- Density and geological properties @ 65 ° C of the ultralight fluid base foamed oil object of this invention freshly prepared in the laboratory and after rolling at 150 ° C and 180 ° C for 5 hours (Conc. PROTEX S-300 = 10 lts m3, Conc. Stabilizer = 10 kgm3).

OBSERVATIONS: 1. - The volume of the foam sample for phase separation was 100 ml. 2 - . 2 - Samples rolled for 18 hr, with 150 psi Nj.

Table No. 2.- Density and geological properties @ 65 ° C of the oil-based ultralight fluid foamed, freshly prepared in the laboratory and after rolling at 150 ° C, and 180 SC for 6 hrs (Conc. PROTEX S-300 = 50 lts m5 and Stabilizer = 10 g / m3).

OBSERVATIONS: 1. - The volume of the foam sample for phase separation was 100 ml.

Table No.3.- Density and geological properties @ 65 ° C of the ultralight fluid base foamed oil freshly prepared in the laboratory and after rolling at 150 ° C, 6 hrs and 180 ° C for 18 hrs (Conc. PROTEX S-300 = 30 lts / Tn3 and Stabilizer = 30 Kg / mJ).

Table No. 4.- Density and geological properties @ 65 ° C of the ultralight base oil foamed freshly prepared in the laboratory, contaminated with NaCl brine, crude oil and COz, before and after rolling at 150 ° C for 6 hrs (Conc Protex S-300 = 50 Its / m3 'Stabilizer Conc. 10 kg / m3).

OBSERVATIONS: 1. - After rolling the foam is stable in all the samples, and the drainage of the liquid phase was presented only in the sample with crude oil at the resting hours, observing only one volume of oil separated from 8 ml (8.0% vol) . 2. · The sample contaminated with brine showed a drainage of the liquid phase of 2 ml after 26 hr of rest. 3. · The volume of the foam sample for phase separation was 100 ml.

Table No. 5 - Density and rheological properties @ 65"C of the ultralight base oil foamed freshly prepared in the laboratory, contaminated with Nací brine, CC½ and perforation cuttings, rolled at 150 ° C for 6 hrs and at 180 ° C for 18 hrs (Conc. Protex S-300 = 30 lts mJ'Conc. Stabilizer 30 kg / m3).

OBSERVATIONS: 1. - The volume of the foam sample for phase separation was 100 ml.

Table No. 6.- Density and Theological properties @ 65 ° C of the ultra-light foamed oil fluid freshly prepared in the laboratory, contaminated with NaCl brine, C02 and perforation cuttings, rolled at 150 ° C for 6 hrs and at 180 ° C for 18 hrs (Protex S-300 Conc = 30 lts m3 'Stabilizer Conc. 30 kg / m3).

OBSERVATIONS: 1. - The volume of the foam sample for phase separation was 500 ml.

For the preparation of the ultra-light foamed oil base fluid, a Hamilton Beach type agitator was used, mixing the products in the following order: Diesel-stabilizing agent-foaming agent shaking at low speed for 15 minutes with the stabilizing agent and 10 minutes with the foaming agent at high speed. The tests of rheological behavior were carried out in a rotational viscometer of coaxial cylinders at a temperature of 65 ° C.

The thermal stability tests were carried out by means of an aging test at a temperature for a certain time, using stainless steel cells of 500 ml capacity and pressurizing with an inert gas (nitrogen) at 150 psig using a heating medium as a heating medium. 6 rollers furnace enabled with temperature controller with PID control mode (Proportional-Integral-Differential).

The stability of the foam was determined by emptying a volume of the foamed ultralight fluid in a 100, 250 or 500 ml specimen and measuring the amount of liquid phase separated at the bottom of the specimen for a certain time.

Pollution tests were carried out by adding a certain amount of the contaminant to the ultra-light base oil foamed fluid and measuring the rheological and drainage properties before and after subjecting them to an aging process at temperature. The pollutant concentrations used were the following: Salt water (saturated NaCl brine = 50 l / m3 Crude oil = 50 lt / m3 Carbon dioxide (C02) = 250 psi in rolling cell 500 ml Drill cuttings (creamy marls) = 5% vol.

The density value reported in the laboratory tests is obtained through the agitation process where the air is occluded by effects of the shape of the propeller and speed with which the fluid is agitated, this value can be modified depending on the the amount of gas (nitrogen, air, or others) that is injected into the mixture by passing it through a foam generator as described in the patent application PA / a / 2003/002391. The density reported in the examples was obtained at room temperature and atmospheric pressure by weighing a volume of 100 ml of the ultra-light foamed oil-based fluid, using a granatary balance with an approximation of 0.1 g and a 100-ml specimen.

While the invention may be susceptible to various modifications and alternative forms, the specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Instead, the invention seeks to cover all modifications, equivalents and alternatives that fall within the spirit and scope of the invention as defined by the following appended claims.

Claims (19)

1. - An improved foaming composition for drilling depressed oil fields formulated mainly with a base oil, a foaming agent, a stabilizer and a gas that is injected into the liquid composition to produce an ultra-light foamed oil-based fluid, characterized in that: the stabilizer, in combination with the foaming agent and the base oil, produce a synergy effect that in a state of rest the foaming composition presents a thixotropic behavior in such a way that it constructs a gelatinous structure that traps the gas bubble preventing it from migrating towards the surface increasing its stability and consequently increases its half-life time; Y wherein the foaming composition allows, when the gas is injected, to form a stable foam at temperatures above 200 ° C.

2. - The foaming composition of claim 1, wherein the foaming agent consists of a non-ionic polymeric foaming agent of the partially perfluorinated acrylic type soluble in non-polar solvents and more specifically in oils of vegetable, mineral, synthetic or hydrocarbon derivatives.

3. - The foaming composition of claim 2, wherein the foaming agent is used in the composition in a concentration that can vary from 0.1 to 5% by volume.

4. - The foaming composition of claim 1, wherein the base oil can be selected from the group of kerosene oils, crude oil, diesel oil, mineral oil, vegetable oil or hydrocarbon condensates and more specifically diesel oil.

5. - The foaming composition of claim 4, wherein the base oil forms part of the foaming composition in a concentration range that can vary from 85% and up to 99% by volume.

6. - The foaming composition of claim 1, wherein the stabilizer used can be selected from the group of ammonium bentonite derived from dimethyl dihydrogenated tallow, ammonium bentonite derived from the dimethyl benzyl hydrogenated bait.

7. - The foaming composition of claim 6, because it employs the stabilizer in concentrations of 5 to 50 kg / m3 taking as a basis for calculation the volume of the foaming composition.

8. - The foaming composition of claim 1, wherein the gas can be membrane nitrogen, cryogenic nitrogen, air, nitrous oxide, argon, helium, xenon, among others.

9. - The foaming composition of claim 1, by virtue of which the synergy that derives from the combination of the base oil-foaming agent-stabilizer allows the stability of the ultra-light foamed oil-based fluid to be improved to the extent that it undergoes for the purposes of temperature, higher temperature, longer half-life, this is because the film thickness of the foaming agent that forms at the gas-continuous phase interface (oil with stabilizer) does not deteriorate under the effects of temperatures above 200 ° C.

10. - The foaming composition of claim 1, because the average life time of the ultralight foamed oil-based fluid also increases as the concentration of foaming agent increases.

11. - The foaming composition of claim 1, by virtue of which it allows the ultra-light foamed oil-based fluid to resist the most typical contaminations found when drilling depressed oil fields and more specifically contaminations with forming water (salt water), dioxide carbon, crude oil, cement, drilling solids (limestones, dolomites, shales, marls, illites, smectites, sands, among others), this derived from the fact that there is no chemical reaction between these pollutants and the components of the ultralight fluid object of this invention.

12. - The foaming composition of claim 1, because after being contaminated and thermally aged for up to 18 hours its properties of half-life and physicochemical properties are not affected thereby ensuring that the ultralight foamed oil-based fluid object of this invention complies with all its functions for the drilling of depressed oil fields.

13. - The method of drilling depressed oil fields which includes an improved foaming composition of the ultralight foamed oil base fluid composed of a base oil, a foaming agent and a stabilizer in varying concentrations according to the density required to drill the depressed fields and According to the average life time of the ultralight fluid that you want to handle, the drilling method consists of: injecting a gas into the foaming composition, which when mixed in a foam generator produces a homogeneous foam with average life times of more than 20 minutes, and up to 10 hours or more; injecting air into sludge dams through the foam diffuser with the purpose of reducing the density of the ultralight fluid to values up to 0.3 g / cm3; pumping by means of a disk pump to feed the suction of a sludge pump in order to avoid the cavitation problems presented by the mud pumps when sucking fluids with a low density (less than 0.7 g / cm3); pump the ultralight foamed fluid base oil through the foam generator, a drilling string, an auger, an annular space and return to a unit under balance, a rotary head, an accelerator, a gas-sludge separator equipment, a control of solids and dams.

14. - The drilling method of claim 13, because it does not require the use of defoamers to keep the ultra-light fluid controlled, avoiding spills and cavitation problems of the pumps.

15. - The drilling method of claim 13, because it allows to use the ultralight foamed oil-based fluid individually (standard drilling) to drill the depressed oil fields or in combination with the drilling method under balance or with controlled pressure.

16. - The piercing method of claim 13, further comprising: employ a solids control device, a degasser and a gas separator to increase the density of the ultralight foamed fluid without the need to use defoaming or defoaming agents.

17. - The drilling method of claim 13, wherein the ultralight foamed oil-based fluid inhibits the hydration of the inflatable shales and flaky shales (rock-fluid interaction) thereby avoiding the occurrence of the perforation problems associated with this problem during the drilling of depressed oil fields.

18. - A foam diffuser characterized in that it is constituted with a pipe closed by one of its ends and in the other is coupled to a hose by means of which a gas flow is circulated that circulates inside the pipe and It comes out through a plurality of holes that are perfectly distributed along the body of the pipe.

19. The foam diffuser of claim 18, wherein the plurality of holes are round in shape and may be of different diameters or of only one, and the length of the pipe may be variable. SUMMARY The present invention relates to an improved composition, preparation and application of an ultra-light foaming oil-based drilling fluid, with average life times of more than 10 hours, for drilling depressed oil fields, where there are active and deleterious clay bodies, and that also present temperatures higher than 180 ° C. The ultra-light fluid resists saltwater contamination, crude oil, acid gases, cement and perforation cuttings. This fluid can be used for drilling, repair and completion of wells using the method of Drilling Under Balance, or Drilling with Controlled Pressure or the traditional method of drilling using a gas (nitrogen, air, among others). It uses a foam generator and / or a diffuser individually or in combination to reduce the specific gravity of the fluid to values less than 0.2. and it can be pumped into the well. A novel aspect of the invention is that the stability of the fluid is improved when subjected to the effects of temperature and can be pumped into the well without cavitation problems through the use of a disk pump connected to the suction of the pumps. sludge