CN1375615A - Method of regulating water sucking sectino of deep oil layer - Google Patents

Abstract

The invention relates to a method in the field of oil exploitation, which can realize the adjustment of the deep water absorption profile of the oil reservoir in the oil field, so that the unproduced crude oil can be driven out during the process of water flooding or polymer flooding, and the method for further improving the recovery rate of crude oil. The method comprises the process of injecting a cross-linked polymer solution into a water injection well, wherein the cross-linked polymer solution is a dispersion of elastic solid and/or non-solid particles formed by a cross-linking agent solution and a polymer solution in water system, or the dispersion system of polymer coils cross-linked by cross-linking agent solution and polymer solution in water, the elastic solid and/or non-solid particles in the dispersion system, or the diameter of cross-linked polymer coils is within 10 -2000nm, and the viscosity of the dispersion system is 0.6-8.9mPa.s.

Description

Method of Adjusting Water Absorption Profile in Deep Reservoir

field of invention

The present invention relates to the field of petroleum exploitation, in particular to a method that can realize the adjustment of the deep water absorption profile of the oil reservoir in the oilfield, so that the unproduced crude oil can be driven out in the process of water flooding or polymer flooding, and the crude oil recovery can be further improved. yield method.

Background of the invention

In the process of oil recovery, oil displacement is an important part of enhanced oil recovery. The traditional methods include water flooding and chemical flooding. Looking at the traditional oil flooding process, it can be found that due to the heterogeneity of the formation, the effect of this oil flooding method is that the crude oil in the rock formation with higher permeability can be driven out smoothly, while the crude oil in the rock formation with lower permeability can be driven out smoothly. Crude oil remains in the ground. For oilfields developed by water flooding for a long time, due to water flushing and clay loss, the permeability of higher permeability formations is further increased, so that the injected water often flows along the high permeability layer, but does not reach the oil-bearing low permeability layer. This low-efficiency water injection not only affects the degree of crude oil recovery, but also increases the cost of oil recovery due to energy consumption, treatment of produced fluid, and corrosion of pipelines.

In order to solve the above problems, technicians have conducted a lot of research and exploration on the technology of adjusting the water absorption profile in the deep part of the oil layer for many years. In addition to mechanical methods, cement slurry was used as a water plugging and profile control agent before the 1960s, and then oil-based cement, lime milk, resin, active heavy oil, etc. were developed, mostly resin, and water-soluble in the 1970s. Polymer gels have begun to be used in oil fields. The use of polymer gels (polymer concentration at 3000-6000mg/L) has played a certain role in improving oil production, but has limited effect on improving the recovery of water flooding reservoirs. . In practice, it has also been found that the application of these technologies can only adjust the reservoir profile within 15 meters from the water injection well under normal circumstances. The adjustment of water absorption profile of other reservoirs) and the adjustment of large sweeping profile are still unresolved.

Since the 1990s, with the popularization and application of polymer flooding technology, new issues have been raised, that is, the heterogeneity of reservoirs after polymer flooding has increased, and the problem of water channeling has become more prominent. How to further expand the swept profile of the displacement fluid after polymer flooding and further increase the oil recovery rate has become another new problem to be solved urgently.

The adjustment of the deep water absorption profile of the reservoir in each period is completed by injecting the profile control agent. During the injection process of the profile control agent, the traditional methods include: 1. Inject the pre-prepared profile control agent from the water injection well. Traditional profile control agents pursue high viscosity or high strength (such as polymer gel), and the polymer concentration used is high to form a network structure, resulting in high injection pressure and difficult injection; 2. "Double liquid method" injection , this method is to inject the polymer solution from the water injection well first, and then inject the cross-linking agent from the same water injection well after a period of time (usually a few days). It is hoped that the polymer and the cross-linking agent will meet and cross-link in the deep formation. However, due to the influence of factors such as the adsorption loss of the cross-linking agent in the formation and the slow diffusion into the polymer solution, it is difficult for the polymer and the cross-linking agent to form a gel in the formation, so it is not as expected 3. Using the "delayed cross-linking method", this method is to wrap the cross-linking agent in "capsules", mix the capsules in the polymer solution, and inject the mixture of the capsules and the polymer solution After formation, the capsule is gradually broken to release the cross-linking agent, which makes it cross-link with the polymer to form a polymer gel, which plays the role of deep profile control. However, due to the difficulty in controlling the preparation and rupture time of capsules, this method has not been successfully recorded in field tests.

Contents of the invention

Aiming at the deficiencies of the current oil displacement technology, the present invention provides a new deep reservoir profile control method, which utilizes the formation of a new profile control agent system to expand the sweep profile adjustment of the deep part of the water flooding and polymer flooding reservoirs, The purpose of reducing the water cut of oil production wells and improving oil recovery.

According to the method for adjusting the deep water absorption profile of the oil layer of the present invention, it includes the process of injecting the cross-linked polymer solution into the water injection well, wherein the cross-linked polymer solution is formed by the cross-linking agent solution and the polymer solution in water and has A dispersion system of elastic solids and/or non-solid particles, or a dispersion system of polymer coils crosslinked by a crosslinking agent solution and a polymer solution in water, the elastic solids and/or non-solid particles in the dispersion system, or The diameter of the cross-linked polymer coils is 10-2000nm, and the viscosity of the dispersion system is 0.6-8.9mPa.s.

The advantage of the dispersed system used in the present invention is that the cross-linking agent solution and the polymer solution are injected into the pipeline and formed during the flow process of the formation through an on-site mixing method. In actual operation, the single-liquid method is used to inject the polymer solution and the crosslinking agent solution from the water injection well. The injection water can be clean water or sewage. In the formed dispersion system, the concentration of the polymer is 50-1000 mg/L, and the cross-linking ratio of the polymer to the metal in the cross-linking agent is 5-100 in terms of mass ratio.

According to the method of the present invention, the selected polymer and crosslinking agent material should be able to make it mixed into a profile control agent dispersion system with elastic solid and/or non-solid particles or crosslinked polymer coils, especially with a diameter of 10 -2000nm dispersion system, its viscosity is 0.6-8.9mPa.s, because this dispersion system has special stability characteristics and good flow characteristics. The present invention uses this profile control agent system to realize deep profile control, and its mechanism is to utilize the formed cross-linked polymer elastic solid and/or non-solid particles, or the adsorption of cross-linked polymer coils in formation pore throats , retention, gradually reduce the permeability of high-permeability formations from micro to macro, from near to far, promote the displacement fluid to change the flow direction, and adjust and expand the sweeping profile of the displacement fluid in the deep formation.

Therefore, the use and formation of this profile control agent system is one of the key technologies of the present invention, and the present invention requires that the selected and used cross-linking agent and polymer should be materials that can form this profile control agent system. The crosslinking agent material can be selected from: aluminum citrate, chromium acetate and organic zirconium; available polymers include: partially hydrolyzed polyacrylamide (HPAM) with a molecular weight of 1 million to 30 million, and the degree of hydrolysis is generally 10-30%. For example, aluminum citrate (AlCit) can be selected as the crosslinking agent, and the polymer can be selected from partially hydrolyzed polyacrylamide (HPAM), with a molecular weight of 1-30 million and a degree of hydrolysis of 10-30%, which are commercially available arrived.

The profile control agent system used in the present invention is formed by fully dispersing the cross-linking agent in the injection water first, and then mixing it with the polymer in the main water injection line under the condition of controlling a certain cross-linking ratio, and then flowing into the formation together. Thereby, the deep part of the oil reservoir can be reached smoothly, which is another key point for realizing the purpose of the present invention.

According to the deep profile control method of the present invention, the concentration of the crosslinking agent solution used for on-site preparation can be 20-100%, the concentration of the polymer solution can be 2000-10000mg/L, and the polymer concentration in the profile control agent system formed by mixing 50-1000mg/L, and the cross-linking ratio (in terms of mass ratio) of the polymer to the metal in the cross-linking agent is 5-100, and the dispersion system is injected into the water injection well. Generally, the mixing process is required to be carried out at a temperature of 10-90°C, and the pH of the injected water is 4-9.

The technical effect of the present invention is: compared with the profile control agent used in the traditional profile control technology, the polymer concentration used in the present invention is greatly reduced, which is beneficial to obtain elastic solid and/or non-solid particles, or cross-linked Dispersion of polymer coils in water. Due to the low viscosity, it is beneficial to enter the depth of the reservoir tens to hundreds of meters through the higher permeability formation (the water channel formed by water flooding or polymer flooding). Due to the adsorption and retention of these elastic solid and/or non-solid particles, or cross-linked polymer coils in formation pores, the permeability of high-permeability formations can be gradually reduced from micro to macro, from near to far , to promote subsequent displacement fluid to change the flow direction, and to displace the crude oil that cannot be driven out by water flooding or polymer flooding in formations with lower permeability (micro or macro), so as to expand the sweeping section of the displacement fluid in the deep formation, The purpose of reducing the water cut of oil production wells and improving oil recovery.

The remarkable effects of the method of the present invention will be further described below in conjunction with specific examples.

Description of drawings

Fig. 1 is a schematic flow chart of the method for adjusting the water absorption profile at the depth of the oil reservoir according to the present invention.

Example

The on-site preparation and injection process of the profile control agent system can refer to the flow chart in Figure 1:

First, pump 20-100% aluminum citrate solution (cross-linking agent) into the main water injection line, and flow through the mixer together with injection water (clean water or sewage) to fully disperse the cross-linking agent; %, the polyacrylamide (polymer) solution with a molecular weight of 100-30 million is imported into the main water injection line with a pump, and the concentration of the polymer and the crosslinking ratio are controlled, and mixed and prepared to become the profile control agent dispersion system for profile control of the present invention. The profile control agent is injected into the water injection well (the above method is the so-called single liquid injection method).

The temperature of the mixing process is controlled at 10-90°C, and the pH of the injected water is 4-9. Mine test one:

The test well group includes 1 water injection well and 4 production wells. Before the test, oil production was performed by water flooding. The polymer concentration injected into the profile control agent system is 160-250mg/L, the cross-linking ratio is 20:1, and it is prepared with clear water. During the 3-month test period, the water content of effective production wells decreased from 85% to 75%, and the daily crude oil production increased by 40%. The profile control range of the profile control agent is calculated to be more than 60 meters away from the water injection well. Mine test two:

The test well group includes 1 water injection well and 5 production wells. Before the test, oil production was performed by water flooding. The polymer concentration injected into the profile control agent system is 200mg/L, the cross-linking ratio is 10:1, and it is prepared with sewage. During the 10-month test period, the water content of the test well group (production well) dropped from 81% to 63%, a drop of 18 percentage points, and the average daily oil production increased from 10.6 tons before the test to 22 tons, and the oil increase rate was 107%. The profile control range of the profile control agent system is calculated to be more than 80 meters away from the water injection well. Mine test three:

The test block includes 4 water injection wells and 11 production wells, which experienced water flooding-polymer flooding-water flooding before the test. Before the test started, the effect of polymer flooding had disappeared, and the water cut rose sharply and rapidly. The polymer concentration in the prepared profile control agent system was 200-400mg/L, and the cross-linking ratio was 20:1-10:1. It was prepared with clean water in the first 7 months of the test, and with sewage in the next 6 months. A total of 13 months Inject profile control agent solution 0.1Pv (pore volume).

During the test period, the average injection pressure of the injection well increased by 2.5MPa, the high permeability layer was blocked, the conflict between layers was effectively improved, the flow direction of the injected water changed significantly on the plane, and the profile control range of the profile control agent was separated from the injection zone. The water well is about 100 meters above; the water cut in the test block and the central well has been declining or fluctuating for 14-19 consecutive months, and the rapid rise in water cut has been effectively controlled; the oil production has rebounded significantly, reaching or exceeding the test start at the highest point The previous level has achieved obvious oil-increasing effect. 20 months after the start, compared with water flooding, the deep profile control effect has increased the recovery rate by 1.5%, increased oil production by 24,700 tons, and increased oil production by 38%, with an input-output ratio of 1:11.

Claims (6)

1, adjusts the method for oil reservoir deep intake profile, comprise in water injection well and to inject the dispersion that is cross-linked to form at water by cross-linking agent solution and polymer solution or by the dispersion of the crosslinked polymer coil of cross-linking agent solution and polymer solution at water with elastic solid (Hookean body) and/or non-solid particulate, elastic solid (Hookean body) in this dispersion and/or non-solid particulate or crosslinked polymer coil diameter are at 10-2000nm, and the viscosity of this dispersion is 0.6-8.9mPa.s.

2, the described method of claim 1, wherein, described dispersion is to inject cross-linking agent solution and polymer solution by on-the-spot on-line mixing mode, makes it the profile control agent dispersion that forms in pipeline and stratum flow process.

3, claim 1 or 2 described methods wherein, are scattered in cross-linking agent solution earlier and inject water, polymer solution are mixed being injected into water injection well again with this injection water.

4, the described method of claim 3 wherein, hands over glue crosslinking agent to be selected from aluminium citrate, chromic acetate, organic zirconium; Polymer is the partially hydrolyzed polyacrylamide (PHPA) of molecular weight 100-3000 ten thousand.

5, claim 1 or 2 described methods, wherein, in formed dispersion, metal crosslinked ratio by quality ratio is 5-100 among the concentration 50-1000mg/L of polymer, polymer and crosslinking agent.

6, claim 1 or 2 described methods, wherein, the cross-linking agent solution concentration of using is 20-100%, polymer solution concentration is 2000-10000mg/L, and metal crosslinked ratio by quality ratio is 5-100 in polymer and the crosslinking agent.

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