Study On Fracturing And CO₂ Huff And Puff Parameters Optimization Of Tight Reservoir In DES Block

Tight oil is a hot topic in unconventional oil and gas development.The tight oil reservoir has the characteristics of poor reservoir physical properties,wide distribution area and low reservoir richness.This paper mainly studies the feasibility of applying carbon dioxide to the development of tight oil reservoirs.On the one hand,carbon dioxide is a greenhouse gas.On the other hand,carbon dioxide can react with crude oil in the formation,which has better development prospects and economic benefits than conventional hydraulic fracturing.This paper takes DES block as an example and mainly carries out the following research work:（1）Collect relevant dynamic and static geological reservoir data,analyze reservoir geological characteristics and development characteristics,and determine the problems that may be encountered in the current development process.（2）Based on the reservoir numerical simulation component model established by the Eclipse reservoir numerical simulation software E300 module,the sensitivity parameters of CO₂ fracturing in vertical and horizontal Wells were optimized by single factor analysis method and multi-factor analysis method,and the optimal values of each influencing factor and its main controlling factors were determined.The research shows that:1)productivity of production Wells increases with the increase of main fracture length,secondary fracture length and conductivity,and the growth trend gradually decreases.2)productivity of production Wells decreases with the increase of fracture spacing,and the decreasing trend gradually increases.3)through multi-factor analysis（orthogonal test-range analysis method,orthogonal test-variance analysis method,information content analysis method,and gray relational degree method）,the main controlling factors affecting fracturing effect are determined:the main crack half length>conductivity ability>secondary crack half length>secondary crack spacing.（3）Single factor analysis method and multi-factor analysis method were used to optimize and analyze various production parameters,and the optimal value and main control factors of each production parameter in the process of carbon dioxide huff and puff were determined.The research found that:I)there is an inflection point in the relationship curves of gas injection amount,gas injection speed,soaking time,oil increase and oil change rate,that is,there is an optimal value.2)huff and puff cycles vary from well to well,generally no more than 4 cycles.3)through multi-factor analysis（orthogonal test-range analysis,orthogonal test-variance analysis,information analysis,gray relational degree method）,the main controlling factors affecting the throughput effect are determined:gas injection volume>gas injection rate>soaking time.The influence of gas injection is much greater than the other two,and the influence of soaking time is very small.（4）Using the economic evaluation method to conduct economic evaluation research on the research block,and determine the net present value,net present value ratio,internal rate of return and dynamic investment payback period of the block.