Simulation Of Complex Fracture Network And Optimization Of CO₂ Huff-n-puff Parameters For Compact Reservoir In Block S7

The exploration and development of compact reservoirs has gradually become an important direction for resource replacement and increasing reserves and production.In recent years,the breakthrough of multi-stage fracturing horizontal well technology provides effective technical support for the development of compact reservoirs.However,short stable production period,rapid production decline and low recovery factor are the main contradictions that can not be avoided in the development of compact reservoirs at this stage by relying on natural energy after fracturing.Through literature investigation,it is found that CO₂huff-n-puff is an effective replacement mode and energy supplement mode suitable for S7 block after staged fracturing elastic development.The physical simulation experiment of multi-round CO₂huff-n-puff in staged fracturing horizontal well is carried out.In the process of CO₂dissolving in crude oil,the volume of crude oil expands,which can effectively supplement formation energy.The existence of fracture provides a dominant channel for CO₂huff-n-puff,and the gas moves along the fracture direction and then diffuses to the matrix around the fracture.The longer the fracture half-length is,the faster the diffusion rate of CO₂is.Soaking well makes CO₂fully contact with crude oil,and the matrix and fracture continuously exchange substances to finally reach balance,effectively reducing the surface tension between CO₂and crude oil and improving sweep efficiency.The cumulative oil recovery percentage increases with the increase of huff-n-puff cycles,but the single-cycle throughput recovery and oil change rate gradually decrease,and three rounds are considered the best throughput rounds in combination with economic evaluation.Using core experimental data and logging data to obtain P-wave and S-wave moveout,and combining with empirical formula to study one-dimensional rock mechanics parameters of single well.On the basis of fine geological modeling,three-dimensional geomechanical integrated simulation is completed by stratified and lithofacies controlled Gaussian function stochastic simulation method,and three-dimensional distribution of reservoir pressure field and stress field is obtained.The difficulties of numerical simulation of CO₂huff-n-puff after fracturing in compact reservoir are as follows:Characterization of complex fracture network and simulation of bidirectional flow of injected medium in fracture and matrix.In this paper,taking S7 block as an example,the traditional reservoir seepage simulation and geomechanics simulation are combined to establish a fluid-solid coupling numerical model.Considering the interaction between artificial fractures and natural fractures combined with micro-seismic monitoring data,the shape of artificial fractures in 12 horizontal wells in S7block is accurately characterized,the distribution of artificial fractures is accurately predicted,and the process of fracture propagation and proppant migration is simulated.On the basis of production performance matching,the component model of a dual-porosity and dual-permeability is established.The multiphase flow of underground fluid after fracturing in tight reservoir is simulated and the productivity after fracturing is matched.The numerical simulation of CO₂huff-n-puff after fracturing in horizontal well in S7 block of western Damintun sag is carried out.The optimal values of production parameters in the process of CO₂huff-n-puff are determined,and the development effect is predicted and compared.The best scheme is that the cyclic injection rate is 7000t,the gas injection rate is 140t/day,the soaking time is 40 days,and the cyclic stimulation is 3 cycles when the formation pressure is restored to 80%.Compared with the original production index,the cumulative oil increment of single well in this scheme is 27553.7m3,and the cumulative recovery degree is increased by 8.02%.