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CN-122014191-A - Alternate pressure-driving oil extraction method for low-permeability reservoir

CN122014191ACN 122014191 ACN122014191 ACN 122014191ACN-122014191-A

Abstract

The invention relates to an alternate pressure-driven oil extraction method for a low-permeability reservoir, and belongs to the technical field of exploration and development of low-permeability reservoirs. The invention provides an oil extraction method of carbon dioxide/water alternate pressure flooding injection of a low permeability reservoir. The stratum is enabled to quickly reach the minimum miscible pressure of carbon dioxide and crude oil through carbon dioxide/water alternate pressure driving, micro cracks are formed in the stratum and are continuously expanded into complex cracks, the seepage capability of the reservoir is improved, meanwhile, water vapor alternate formation is conducted to achieve a Jack effect to control fluidity, water channeling and gas channeling are controlled, meanwhile, carbon dioxide is dissolved in water to form an acidic corrosion pore canal, and the permeability of the reservoir is increased.

Inventors

  • NIU BAOLUN
  • WU SHA
  • LIU QIONG
  • XUE YONGXIN
  • XU HAIMIN
  • ZHOU XUN

Assignees

  • 中国石油化工股份有限公司
  • 中国石油化工股份有限公司中原油田分公司

Dates

Publication Date
20260512
Application Date
20241111

Claims (8)

  1. 1. The alternating pressure-driven oil extraction method for the low-permeability oil reservoir is characterized by comprising the following steps of: (1) Obtaining a total injection amount of the pressure flooding based on the target oil reservoir comprehensive compression coefficient, the oil reservoir volume, the expected recovery formation pressure and the current formation pressure; (2) Constructing a three-dimensional numerical model based on physical properties of a target oil reservoir and formation fluid properties, respectively determining the corresponding relation between the injection speed of water or carbon dioxide and the recovery degree under the constraint of the total injection amount of the pressure flooding and the micro-fracture pressure of the formation, and selecting the optimal injection speed; (3) Determining the optimal alternate slug injection amount and volume ratio by utilizing the total injection amount of the pressure flooding obtained in the step (1) and the optimal injection speed obtained in the step (2); (4) And (3) according to the optimal injection speed obtained in the step (2) and the optimal alternative slug injection quantity and volume ratio obtained in the step (3), alternately driving water and carbon dioxide by slug pressure, stopping injection after the total injection quantity of the injection pressure is injected, closing an injection well, and starting oil well production when the oil pressure change rate of a target oil well is less than or equal to 0.1 MPa/d.
  2. 2. The method for alternately fracturing and driving oil recovery of the low permeability reservoir according to claim 1, wherein the calculation formula of the total injection amount of the fracturing and driving is Q Pressure drive ＝C t V(P Target object -P At present , wherein Q Pressure drive is the total injection amount of the fracturing and driving, m 3 ;C t is the comprehensive compression coefficient, MPa -1 , V is the volume of the reservoir, m 3 ;P Target object is the expected recovery formation pressure, MPa, and P At present is the current formation pressure, MPa.
  3. 3. The method for alternately pressure-flooding oil recovery of a low permeability reservoir according to claim 2, wherein P Target object is 1.3-1.6 times of the minimum miscible pressure of crude oil and carbon dioxide of a target oil well.
  4. 4. The method for alternately pressure-flooding oil recovery of a low permeability reservoir according to claim 1, wherein the formation micro-fracturing pressure comprises water injection formation micro-fracturing pressure P w1 and carbon dioxide injection formation micro-fracturing pressure P w2 , P w1 is 0.8-0.95 times of water injection formation fracturing pressure P Rupture of 1 , and P w2 is 0.8-0.95 times of carbon dioxide injection formation fracturing pressure P Rupture of 2 .
  5. 5. The method for alternately pressure-flooding oil recovery of the low permeability reservoir according to claim 2 or 3, wherein the calculation formula of V is as follows: wherein V is the volume of the oil reservoir, m 3 , N is the geological reserve, m 3 ; Porosity, S oi is original oil saturation, and K is high-pressure hole expansion rate.
  6. 6. The method for alternately pressing and driving oil recovery of low permeability reservoir according to claim 5, wherein K is 0.5-1%.
  7. 7. The method for alternately pressing and driving oil recovery of low permeability reservoir according to claim 6, wherein the calculation formula of the comprehensive compression coefficient is: Wherein C f is the rock compression coefficient, MPa -1 ;C o is the oil compression coefficient, MPa -1 ;C W is the water compression coefficient, MPa -1 ;S oi is the original oil saturation, S wi is the irreducible water saturation; porosity, K is high-pressure hole expansion rate.
  8. 8. The alternating pressure flooding oil extraction method of the low permeability oil reservoir according to any one of claims 1-4, wherein the average permeability of the low permeability oil reservoir is less than 10.0×10 -3 μm 2 .

Description

Alternate pressure-driving oil extraction method for low-permeability reservoir Technical Field The invention relates to an alternate pressure-driven oil extraction method for a low-permeability reservoir, and belongs to the technical field of exploration and development of low-permeability reservoirs. Background Low permeability reservoirs (also known as low permeability fields) are fields in which the reservoir permeability of the reservoir is low, the abundance is low, and the single well capacity is low. There is no unified standard and limit for low permeability oil fields in the world, but a relative concept, different countries are formulated according to different periods of petroleum resource conditions and technical and economic conditions, and the variation range is large. Luo Zhetan, wang Yuncheng (1986) to divide an oil layer having a permeability of less than 100X 10 -3μm2 into low permeability oil layers, yan Hengwen et al (1993) to divide a reservoir having a permeability of less than (10-100) X10 -3μm2 into low permeability reservoirs, (0.1-10) X10 -3μm2 being a specific permeability reservoir, tang Zengxiong (1994) to divide a low permeability oilfield reservoir having a permeability of (10-100) X10 -3μm2 of less than 10X 10 -3μm2 being an ultra low permeability oilfield. However, li Daopin et al (1997) proposed that reservoirs with permeability of (0.1-50) x 10 -3μm2 are generally referred to as low permeability reservoirs, and according to practical production characteristics, low permeability fields are further classified into three categories according to the average permeability of the reservoirs, wherein the first category is a general low permeability field, the average permeability of the reservoirs is (10.1-50) x 10 -3μm2, the second category is an extremely low permeability field, the average permeability of the reservoirs is (1.1-10) x 10 -3μm2, the third category is an extremely low permeability field, and the average permeability of the reservoirs is (0.1-1) x 10 -3μm2, but such reservoirs are very dense, have high irreducible water saturation, have no natural productivity basically, and generally do not have industrial development value. The low-permeability oil and gas field has important significance in oil and gas development in China, the low-permeability oil and gas field found in China accounts for more than half of newly found oil and gas reservoirs, the scale of the capacity construction of the low-permeability oil and gas field accounts for more than 70% of the total scale of the capacity construction of the oil and gas field, and the low-permeability oil and gas field becomes a main battlefield of the oil and gas development construction. Moreover, the low-permeability oil and gas resource distribution in China has the characteristics of more oil and gas, more oil and gas reservoir types and wide distribution area, and the low-permeability oil and gas reservoir reserves have high proportion in the ascertained reserves, which account for more than 2/3 of the national reserves, and have huge development potential. But many problems to be solved are faced to achieve cost effective development of low permeability fields. Because the low permeability field is not a formation reservoir, but a lithologic formation reservoir, the exploration difficulty is great. During exploration, how to accurately know the distribution rule of a low-permeability oil and gas field, control the area of the low-permeability oil and gas field, search for an oil and gas enrichment area and the like are all problems needing to be continuously researched. Moreover, after the low permeability oil reservoir is accurately explored, the natural energy is insufficient due to the characteristics of low abundance and low pressure of the low permeability oil field, so that the natural yield of the oil well is very low. Therefore, the improvement of the single well yield of the oil and gas field through technical innovation is also a problem to be solved. The water flooding technology is a development mode commonly used for low-permeability oil reservoirs, and the principle is that the pressure of an oil layer is increased by injecting a large amount of water, so that the oil in the oil reservoir is pushed to migrate to a wellhead, and the productivity is improved. The low-permeability reservoir is injected with pressure flooding water, so that the oil-water well is injected with water at high pressure rapidly, the stratum energy is increased, the pressure flooding increases the rock pore pressure, micro cracks are formed in the near well, the micro cracks are gradually gathered to form a main crack zone, the seepage capability of the reservoir can be greatly increased, but the pressure flooding water flooding micro cracks are smaller in range, complex micro cracks cannot be formed, crude oil in pores with the diameter of more than 0.1 mu m in the micro cracks can be displaced, meanwhile, water channelin