阅读说明：本技术 针对细粉砂用高分子与低分子聚合物相结合的防砂体系 (Sand control system combining high molecules and low-molecular polymers for fine silt ) 是由 张殿印 史胜龙 温庆志 张东晓 于 2020-06-16 设计创作，主要内容包括：本发明提供一种针对细粉砂用高分子与低分子聚合物相结合的防砂体系,包括高分子聚合物体系和低分子聚合物体系,高分子聚合物体系和低分子聚合物体系的体积比为1：1.25～8；所述防砂体系在使用时,按照先低分子聚合物体系,后高分子聚合物体系的注入顺序注入地层。低分子聚合物能使细粉砂自聚成砂团,之后通过高聚物形成具有一定强度的高弹性高渗透率的挡砂屏障,能有效解决细粉砂的出砂问题。高分子与低分子聚合物相结合的防砂体系,溶液性能稳定,安全环保、现场施工程序少,工作量低,且注入工序简单,适用于粒径低于100μm的细粉砂出砂问题。该防砂体系中不含固体成分,不含树脂,所含高分子与低分子聚合物的成本低、原材料来源广。(The invention provides a sand control system combining high molecules and low molecules for fine silt, which comprises a high molecule polymer system and a low molecule polymer system, wherein the volume ratio of the high molecule polymer system to the low molecule polymer system is 1: 1.25-8; when the sand control system is used, the low molecular polymer system is injected into the stratum in the injection sequence of the high molecular polymer system. The low molecular polymer can lead the fine silt to be self-polymerized into a sand cluster, and then a high-elasticity high-permeability sand blocking barrier with certain strength is formed by the high polymer, so that the problem of sand production of the fine silt can be effectively solved. The sand control system combining the high polymer and the low molecular polymer has stable solution performance, safety, environmental protection, less field construction procedures, low workload and simple injection process, and is suitable for the problem of sand production of fine silt with the particle size of less than 100 mu m. The sand control system does not contain solid components and resin, and contains high molecular and low molecular polymers with low cost and wide raw material sources.)

1. The sand control system combining the high molecules and the low molecules for the fine silt is characterized by comprising a high molecule polymer system and a low molecule polymer system, wherein the volume ratio of the high molecule polymer system to the low molecule polymer system is 1: 1.25-8, and when the sand control system is used, injecting the low-molecular polymer system and the high-molecular polymer system into a stratum according to the injection sequence.

2. The sand control system of claim 1, wherein the polymeric system is an aqueous solution comprising one or more water soluble organic polymeric compounds having a viscosity of 300 to 500mPas when dissolved in water, the organic polymeric compounds having a solubility at room temperature of greater than 2g/100g water; the organic polymer compound can react with cations to form a solid substance with anti-scouring performance.

3. The sand control system according to claim 1, wherein the mass fraction of the organic polymer compound in the polymer system is 0.7-1.5%.

4. The sand control system of any one of claims 1 to 3 wherein the organic polymeric compound is sodium alginate.

5. The sand control system of claim 1 wherein the low molecular polymer system comprises the following components: polyethylene glycol, non-ionic polyacrylamide, potassium chloride and calcium chloride.

6. The sand control system according to any one of claims 1 to 3, wherein the low molecular polymer system comprises 0.1 to 1 mass percent of polyethylene glycol, 0.2 to 4 mass percent of nonionic polyacrylamide, 1 to 20 mass percent of potassium chloride, 0.5 to 5 mass percent of calcium chloride, and the balance of water.

7. The sand control system according to claim 6, wherein in the low molecular polymer system, the mass fraction of polyethylene glycol is 0.1-0.3%, the mass fraction of nonionic polyacrylamide is 0.5-1.5%, the mass fraction of potassium chloride is 2-10%, and the mass fraction of calcium chloride is 0.8-3%.

8. The sand control system of claim 5 wherein the polyethylene glycol is one or more of polyethylene glycol 200, polyethylene glycol 400, and polyethylene glycol 600; the molecular weight of the non-ionic polyacrylamide is less than or equal to 100 ten thousand.

9. The use of the sand control system according to any one of claims 1 to 8, characterized in that the method of use comprises the following steps:

(1) injecting a pad fluid into a well, (2) injecting a low-molecular polymer system, (3) injecting a middle slug, and (4) injecting a high-molecular polymer system; (5) and (6) injecting a displacement liquid, and (6) closing the well for 24-72 hours.

10. Use according to claim 9, wherein the low-molecular polymerization system is injected in a quantityThe amount of polymer system injected

Technical Field

The invention belongs to the technical field of oil and gas field development in the petroleum industry, and relates to a sand control system combining high molecules and low molecules of fine silt.

Background

With the continuous development of scientific technology, the generation of new technology also needs raw materials to provide research and development guarantee, petroleum is called liquid gold, and has high political and economic status in each country, and the oil and gas yield of one country can sometimes even determine the status of one country in the world. China is a new big country, the biggest developing countries in the world are particularly important in dependence on petroleum, the petroleum produced in China at present only accounts for 40% of the petroleum consumption in China, other countries need to rely on imports, how to fully develop the oil and gas resources in China is particularly important, national policies also continuously promote the technical research and development of the oil and gas industry, and good technology can generate great economic benefit. Sand production from oil and gas wells is a very common problem throughout the production of oil and gas wells. It is known that over 70% of oil and gas reservoirs are unconsolidated formations in the world, the unconsolidated formations are mostly cemented in a contact mode due to low content of sand cement, sand is easy to separate from rock under the influence of factors influencing formation stress or fluid migration and the like in the production process, and then the sand flows into a shaft along with the fluid, and the phenomenon is sand production. The sand production harm is mainly that the production layer is buried, so that the oil gas yield is reduced; the well bottom and the ground equipment are abraded, so that the development cost is increased; meanwhile, large-area sand production is dangerous, which may cause collapse of the stratum.

The current sand control modes mainly comprise mechanical sand control and chemical sand control, wherein the mechanical sand control comprises the steps of putting a sand control tubular column into a sand production interval and blocking formation sand outside a shaft through a screen. The sand control mode has high requirements on the optimization of the screen, the production capacity is greatly influenced due to too large mesh number, and fine silt gradually blocks the meshes to cause the production stop of the oil and gas well; too small a mesh size will not effectively prevent sand from entering the wellbore. The biggest disadvantage of mechanical sand control is the difficulty in preventing fine silt with small particle size. Chemical sand control is to inject chemical agents into a sand producing stratum to enhance the bonding strength of stratum rocks and form a high-strength sand blocking barrier, but any chemical sand control mode inevitably has certain influence on the permeability of the stratum, so that the optimal chemical agents and good chemical agents are required to be selected and selected, the sand control can be effectively realized, and meanwhile, the influence on the stratum is within an acceptable range. The sand consolidation agent commonly used at home and abroad is a series of products taking resin as a main body, the resin forms a high-strength cementing body at a certain temperature and time by adding a curing agent, the cementing strength of a loose rock stratum can be enhanced, and far sand grains can be blocked at a deeper position of the stratum through a formed sand blocking barrier. However, the resin consolidated sand has poor sand control effect on the fine silt, because the particle size of the fine silt is less than 100 μm, and the resin consolidated sand needs to adhere a layer of film on the surface of the sand grain and then forms strength through cross-linking. However, since the fine silt particles are too small and compact to each other, the viscous liquid such as resin hardly enters the gaps between the fine silt particles, which results in that the fine silt hardly forms a film. Even if a film is formed, because a layer of resin is adhered to the surface of the sand, the resin is solidified and then is in a solid state, so that the increase of the grain size is formed on the surface of the sand, the radius of the sand is increased, the porosity of a stratum is reduced, and the fluid flow is influenced; meanwhile, the specific surface area of the fine sand is large, so that high strength is formed, the dosage of the resin can be increased by several orders of magnitude rapidly, and the sand prevention cost is necessarily greatly increased.

Chinese patent document CN108949132A (201710390271.6) discloses a sand consolidation and plugging removal treatment fluid for sand control of a fine silt reservoir oil well, a sand control treatment fluid system and a sand control method using the sand consolidation and plugging removal treatment fluid, wherein the sand consolidation and plugging removal treatment fluid comprises the following components in percentage by mass: 8-12% of sand-fixing blocking remover, 0.5-1.5% of cleanup additive, 0.5-1.5% of corrosion inhibitor, 1-2% of iron ion stabilizer, 1-2% of mutual solvent, 1-2% of ammonium chloride and the balance of water. The sand control treatment fluid system consists of pretreatment fluid, pre-treatment fluid, treatment fluid and displacement fluid, and the volume ratio of the pretreatment fluid to the treatment fluid is as follows in sequence: 4-6: 1-2: 2-3: 1-2 and also discloses a sand prevention method using the sand prevention treating fluid system. However, the sand control system can pollute a reservoir, and other corrosion inhibitors, stabilizers and the like are added, so that the cured resin material cannot be treated, the permeability of the stratum is reduced, the cured resin can even make the stratum have no liquid production, and the sand control treatment system has no capacity of stabilizing clay expansion and cannot be applied to the stratum with the clay content of more than 10%. The system has the main function of blockage removal, has a common sand control effect and has the possibility of fine silt.

Dupuis et al describe a water-soluble polymer for sand control in offshore wells (SPE-179825-MS) and the copolymer is Powelgel^TMP100, 2% KCl in water. Compared with the traditional resin sand control, the sand control system has the advantages of reducing reservoir damage, being environment-friendly due to a water-based system, not needing additional sand control pipe column construction and the like, and has the advantages of good sand control effect and 100% success rate due to the application of nine wells in the sand control of offshore oil wells. However, since this technique uses a polymer which forms an aggregation effect of sand grains by hydrogen bonding or ionic bonding, migration of sand grains is prevented to reduce sand production. Therefore, under the conditions of higher production pressure difference and larger daily liquid production amount, the effect is not ideal, the field application of the technology is limited to oil wells with low sand production amount at sea, and the application of the method is very limited under the background of the requirement of the current oil company for improving the yield. Therefore, at present, no effective sand control means exists for the fine silt.

Disclosure of Invention

The invention provides a sand control system combining high molecules and low molecules for fine silt, aiming at solving the problems that the sand control effect of fine silt is poor and resin is difficult to effectively solidify the fine silt in the prior art. The sand control system is used for solving the problem of sand production of fine silt with the formation sand grain size of less than 100 mu m. The sand control system can realize self-agglomeration of fine silt, and then enhance the strength of the sand cluster through chemical reaction, so that the formed high-permeability sand cluster is resistant to scouring, and the sand cluster has certain strength and a self-repairing function. The treatment radius of the sand prevention system is 1.5m, so that a sand blocking barrier with enough thickness can be formed, the original stratum property at a distance can not be polluted, and the best construction and production effect is ensured; meanwhile, the anti-swelling agent is added, so that clay expansion can be effectively prevented, and the stratum with the clay content within 40% can play a good sand prevention and fixation effect.

In order to achieve the purpose, the invention adopts the following technical scheme:

a sand control system combining high molecules and low molecules for fine silt comprises a high molecule polymer system and a low molecule polymer system, wherein the volume ratio of the high molecule polymer system to the low molecule polymer system is 1: 1.25-8, and when the sand control system is used, injecting the low-molecular polymer system and the high-molecular polymer system into a stratum according to the injection sequence.

Preferably, the polymer system is an aqueous solution containing one or more water-soluble organic polymer compounds, the viscosity of the organic polymer compounds is 300-500 mPas when the organic polymer compounds are dissolved in water, and the solubility of the organic polymer compounds at room temperature is more than 2g/100g of water; the organic polymer compound can react with cations to form a solid substance with anti-scouring performance. Further preferably, the organic polymer compound is capable of reacting with a divalent cation in water; further preferably, the divalent cation is calcium.

Further preferably, the formed solid substance with the anti-scouring performance is continuously scoured for 2 hours under 1000mL/min of water flow, and the sand yield is lower than 0.02%.

Preferably, the volume ratio of the high molecular polymer system to the low molecular polymer system is 1:1.4 to 8.

Preferably, the mass fraction of the organic polymer compound in the polymer system is 0.7 to 1.5%.

Preferably, the organic polymer compound is sodium alginate.

Preferably, the low molecular weight polymer system comprises the following main constituents: polyethylene glycol, non-ionic polyacrylamide, potassium chloride and calcium chloride.

Preferably, in the low-molecular polymer system, the mass fraction of the polyethylene glycol is 0.1-1%, the mass fraction of the nonionic polyacrylamide is 0.2-4%, the mass fraction of the potassium chloride is 1-20%, the mass fraction of the calcium chloride is 0.5-5%, and the balance is water.

Preferably, in the low-molecular polymer system, the mass fraction of the polyethylene glycol is 0.1-0.3%, the mass fraction of the nonionic polyacrylamide is 0.5-1.5%, the mass fraction of the potassium chloride is 2-10%, and the mass fraction of the calcium chloride is 0.8-3%.

Further preferably, the polyethylene glycol is one or more of polyethylene glycol 200, polyethylene glycol 400 and polyethylene glycol 600; the molecular weight of the non-ionic polyacrylamide is less than or equal to 100 ten thousand.

The polyethylene glycol plays a role in reducing surface tension, is beneficial to reducing the impact of liquid on sand balls, and can improve the liquid yield and the oil yield; the polyacrylamide can realize the self-aggregation of sand grains and is a flocculating agent; the potassium chloride plays a role in preventing clay from swelling, and the calcium chloride plays a role in reacting with the high-molecular polymer.

The fine silt is generally positioned at the far end of the well, the fine silt has electric charges so that mutual repulsion exists, which is the reason why fine particles cannot be agglomerated, and the invention reduces the electric charges on the surface of the fine silt through the treatment fluid (low molecular polymer) so that attraction is carried among the fine silt particles. The polymer with low molecular weight adopted by the invention can be effectively adhered to the surface of sand grains, and the polymer simultaneously has hydroxyl groups, so that the attraction force of the grains per se and hydrogen bonds among the grains can be realized, and self-aggregation can be realized. However, the sand control system treated only by the low molecular polymer has low strength, and the flow velocity is sharply increased in the near wellbore zone due to centripetal flow, so that the self-agglomerated sand agglomerates are easily dispersed and flushed into the near wellbore zone. According to the invention, a high-molecular polymerization system is adopted in a near wellbore zone to realize sand blocking, the high-molecular polymer can form a three-dimensional net structure through chemical reaction, the structural strength reaches the highest in 24-48 hours, and finally a high-strength sand blocking barrier is formed (schematic diagrams are shown as 1 and 2). The permeability of the sand cluster formed by the sand control system is in mum²In the grade, the sand cluster has certain strength and excellent elasticity and can generate plastic deformation under the external pressure, so that the particles in the sand cluster are difficult to separate, and even if the particles are separated from the sand cluster, the particles still have mutual adsorption force and can self-agglomerate for many times. The stability of the sand ball is high, and the sand ball can effectively exist for more than 13 months at 110 ℃. The sand ball is resistant to fluid impactHas better advantages than resin sand control.

The invention adopts low molecular weight polymer to realize self-agglomeration of sand grains, then enhances the strength of the sand grains through the chemical reaction of the high molecular weight polymer, captures the sand grains into agglomerates through formed chemical bonds, has the performances of scouring resistance and high permeability, is clean and environment-friendly in used materials, and passes the certification of the China Committee for national acceptance of China AS (China Committee for qualification). The viscosity is controllable, and the stratum with different permeabilities can be effectively treated.

If only a high molecular polymerization system is used for sand control, firstly, the viscosity is high, so that the treatment radius is low and the sand control effect is poor; secondly, the high molecular polymer has no effect of self-agglomerating the sand aggregates, and the sand grains are in a discrete form, so that the sand grains which are not contacted with the high molecular polymer are easy to block the pores of the stratum, and the permeability is reduced.

When only low-molecular polymer is used for sand prevention, the formed self-polymerized sand cluster has low strength and poor water flow resistance, and the sand cluster is easily dispersed to cause sand production under the condition of high flow rate in a near-well zone.

The invention also provides application of the sand control system, and the application method comprises the following steps:

(1) injecting a pad fluid into a well, (2) injecting a low-molecular polymer system, (3) injecting a middle slug, and (4) injecting a high-molecular polymer system; (5) and (6) injecting a displacement liquid, and (6) closing the well for 24-72 hours.

The volume ratio of the high molecular polymer system to the low molecular polymer system is 1: 1.25 to 8.

The injection amount of the pad fluid is related to the pore volume of the treated stratum, and is generally 1.5m per meter of oil layer³～2m³. The middle slug is related to the whole well depth, generally 2m³～3m³. The injection amount of the displacement liquid is related to the volume of the shaft and the volume of the ground pipeline and is 1-1.2 times of the volume of the shaft and the volume of the ground pipeline.

The total amount is designed according to the injection amount of low-molecular and high-molecular polymers, the porosity, the thickness and the treatment radius of the stratum.

The high molecular processing radius refers to the radius processed by a high molecular polymer, and the total processing radius refers to the total radius processed by the high molecular polymer and a low molecular polymer; the polymer treatment radius is generally 0.3 to 0.7 times of the total treatment radius.

Preferably, the pad fluid, the middle slug and the displacing fluid are all clear water.

The invention has the beneficial effects that:

(1) the invention provides a sand control system combining a high molecular polymer and a low molecular polymer, wherein the low molecular polymer can enable fine silt to be self-polymerized into sand balls, and then a high-elasticity high-permeability sand blocking barrier with certain strength is formed by the high polymer, so that the sand production problem of the fine silt can be effectively solved.

(2) The formed sand ball has good elasticity and fluid impact resistance, and indoor experiments prove that the sand ball is continuously flushed for 2 hours at 1000mL/min, and the sand yield is lower than 0.02 percent.

(3) The sand control system combining the high polymer and the low molecular polymer has stable solution performance, safety, environmental protection, less field construction procedures, low workload and simple injection process, and is suitable for the problem of sand production of fine silt with the particle size of less than 100 mu m.

(4) The sand control system does not contain solid components and resin, and contains high molecules and low molecular polymers with low cost, wide raw material sources and high feasibility.

Drawings

FIG. 1 is a schematic diagram of the sand control principle of the sand control system of the present invention;

FIG. 2 is a schematic diagram of a high molecular polymer mesh-structured sand blocking cluster of the sand control system of the present invention;

FIG. 3 is a cross-sectional view of 200 mesh quartz sand and the formed sand agglomerates;

FIG. 4 is a schematic view of a low molecular weight polymer solution;

FIG. 5 is a schematic view of a high molecular weight polymer solution.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and embodiments.