川中地区侏罗系致密性油藏合理生产压差模拟实验分析  

Simulation experiment of reasonable production pressure difference in Jurassic tight reservoirs,central Sichuan Basin

作　　者：丰妍 李秀清 李雪松 白蓉 余凯 李兰 韩璐媛 FENG Yan;LI Xiuqing;LI Xuesong;BAI Rong;YU Kai;LI Lan;HAN Luyuan(Exploration and Development Research Institute,PetroChina Southwest Oil&Gasfield Company,Chengdu,Sichuan 610041,China)

机构地区：[1]中国石油西南油气田公司勘探开发研究院,四川成都610041

出　　处：《天然气勘探与开发》2024年第6期25-34,共10页Natural Gas Exploration and Development

基　　金：中国石油集团公司攻关性应用性科技专项(编号:2023ZZ15)。

摘　　要：川中地区侏罗系致密性油藏储层属于特低孔隙度特低渗透率,生产过程中表现出启动压力梯度高、应力敏感性强、基质-裂缝双重介质流动的渗流特征,裂缝系统和原油的弹性能是气井生产初期主要驱动能量。合理控制生产压差、降低储层应力敏感伤害、最大程度利用地层综合能量是该类油藏开发的关键。为此,以室内实验为手段,采用致密岩心和含气原油样品,将裂缝岩心和基质岩心串联,模拟压裂改造后井筒近井区和远井区储层环境,开展致密性油藏合理生产压差实验研究。研究结果表明:(1)不稳定流测试阶段主要是裂缝岩块流动,驱替压力小,基质岩块供给滞后,油气产量迅速下降;稳定流测试阶段随实验驱替压差逐渐增大,基质岩心的流体开始向裂缝岩心流动,流量随驱替压差增大会产生一个明显拐点,即产量最大值。(2)当出口端压力低于泡点压力时,地层原油在岩心中脱气,裂缝岩心渗透率越大,渗流能力越强,克服两相渗流阻力的能力越强,油相相对渗透率下降幅度减缓,产出流体气油比上升幅度变缓;油量呈先上升再下降的趋势。(3)随实验驱替压差的增大,单位面积油相渗流速度将开始降低,产量对应的生产压差即为最大合理生产压差。室内实验充分考虑了致密性储层混合润湿和非线性渗流效应,测试结果更加符合现场实际,能有效提高致密性油藏衰竭开采合理生产压差的确定性,为致密性油藏早期单井合理配产提供基础参数和理论依据。The Jurassic tight reservoirs in central Sichuan Basin are featured by ultra-low porosity and permeability.During the production process,the reservoirs show the seepage characteristics of high start-up pressure gradient,strong stress sensitivity,and matrix-fracture dual-medium flow.The fracture system and the elastic energy of crude oil are the main drive in the initial stage of gas well production.Reasonably controlling the production pressure difference,reducing the stress sensitivity damage,and maximizing the utilization of comprehensive formation energy are crucial to the development of such reservoirs.By means of laboratory experiment with tight cores and gas-bearing crude oil samples,fractured core and matrix core were connected in series to simulate the reservoir environment near and far away from wellbore area after fracturing,so as to determine the reasonable production pressure difference in tight reservoirs.The following results are obtained.(i)The simulation test is divided into two stages:unsteady flow test and steady flow test.The former is characterized by fracture-rock flow,low displacement pressure,delay of matrix-rock supply,and rapid decline of oil and gas production.In the latter stage,with the increasing difference of experimental displacement pressure,the fluids in matrix core begin to flow to fractured core,the flow rate exhibits an obvious inflection point with the increase of displacement pressure difference,i.e.,the maximum production.(ii)When the outlet pressure is lower than the bubble point pressure,the in-place oil is degassed in the core.The greater the permeability of the fractured core,the stronger the seepage capacity,and the stronger the ability to overcome the two-phase flow resistance.The decline in the oil-phase relative permeability and the rise in the gas-oil ratio of produced fluids slow down.The oil production shows a trend of first rising then falling.(iii)With the increase of experimental displacement pressure difference,the oil-phase flow velocity per unit area begins

关 键 词：川中地区 侏罗纪 致密性油藏 裂缝岩心 衰竭式开采早期 合理生产压差 

分 类 号：TE312[石油与天然气工程—油气田开发工程]