低渗透油田小井距注CO_2方案优化研究

为解决大情字井油田水驱控制程度低,注水压力高,开采效果差以及长岭气田天然气的脱碳埋存难问题,决定大情字井油田开展小井距CO_2混相驱替试验。为研究CO_2驱油机理,提高注气开发效果,通过数值模拟技术并结合矿场试验,对开发层系划分、井网部署、注入方式、注气速度、气水段塞比以及油井流压等参数进行了优化,确定优化方案如下:确定青一段7、11、12和14小层为注气试验层;采用五点法井网,注采井距为225 m,采用气水交替的方式注入,年注气速度为0.07 HCPV,气水比为1:1,油井流压为12 MPa。经矿场实施结果表明,小井距注CO_2驱替,增油效果明显,并且试验周期短,能有效解决地层压力亏空、水驱见效慢以及砂体控制程度低等问题,并且选择物性相近,具有良好隔层的油层注气,采用气水交替的注入方式可有效抑制小井距易气窜问题,更大程度提高油田采收率。

Study on Optimization of Small Well Spacing CO2Injection Plan in Low Permeability Oilfields

In order to solve the problem of low water flooding control, high water injection pressure, poor production effect and decarburization of natural gas in Changling gas field, the experiment of small well spacing CO2 mixed-phase displacement in Daqingzijing oilfield was carried out. In order to study the mechanism of CO2flooding and improve the effect of gas injection development, the numerical simulation technology and field test were used to optimize the parameters, including development layer division, well pattern deployment, injection mode, gas injection rate, and so on. The optimized scheme was determined as follows: 1, 11, 12, and 14 small layers were set for the gas injection test layer; the five-point well pattern was used, and the well spacing was 225 m; gas and water alternate injection way was used, the annual injection rate was 0.07 HCPV, ratio of gas to water was 1: 1, oil flow pressure was 12 MPa. The implementation results showed that the stimulation effect of small well spacing CO2flooding was obvious, and the test period was short, small well spacing CO2flooding effectively solved the problem of formation pressure deficit, water drive slowness and low control degree of sand body. Choosing the oil layer with similar physical properties and good septum for gas injection, and using gas and water alternating injection method, effectively inhibited the small well spacing gas channeling problem, and oil recovery was increased.