Application Of Coiled Tubing With Bottom Seal Jet Fracturing Technology In Hechuan Block

With the development of petroleum industry,the exploration and exploitation of oil and gas focus more on unconventional resouces which are difficult to develop than the conventional ones.Xujiahe Formation in Hechuan area of Sichuan Basin is a typical unconventional reservoir with strong exploitation difficulties due to the multi-layer and interbedding-layer characteristics.Separate-layer fracturing theory and technology are key to stimulate and make full use of these formations,and maximize the flow rates.However,there are challenges in effectively using this method including poor performance of packers,the lack of pertinence,and significant operation difficulties.Separate-layer fracturing,using coiled tubing with packers,is a technology that incorporates coiled tubing,sealing,perforation and fracturing.This technique can not only achieve massive stimulation but also perform refined separate-layer fracturing.This study analyzes basic characteristics of Xujiahe Formation and summarizes the difficulties in fracturing treatment for these reservoirs.To deal with thin interbedding layers with large span,mathematical models for multi-stage fractured vertical and horizontal wells are established,fracture propagation mechanisms are investigated,and a good understanding of theadaptabilityof different technologies are obtained.By analyzing the mechanism of coiled tubing multi-stage hydraulic jet perforation,multi-stage fracturing techniques are optimized.Besides,this study investigates and designs coiled tubing bottom sealing devices and conducts relative lab experiments with research emphasis on hudrualic jet perforation optimization design,coiled tubing bottom sealing devices design,coiled tubing packer lab experiments and its field application.This technique has been successfully applied in highly-deviated well with thin layers in Xujiahe Formation in Hechuan.Results suggest that the occurrence of coiled tubing annulus-sand-injection fracturing with packers enormously increases the number of stages in multi-stage fracturing for unconventional tight gas,especially for reservoirs with thin interbedding and heterogeneous layers.Compared with traditional coiled tubing fracturing,the pump rate of annulus-sand-injection fracturing is far larger.This thesis provides theoretical basis for the application of coiled tubing annulus-sand-injection,multistage and targeted fracturing in vertical and highly-deviated wells.Experiments,simulation and application show that this method satisfies the design requirements and expectations.This study demonstrates the mechanism,characteristics and field application of coiled tubing multistage fracturing with hydraulic-jet perforation,summarizes potential risks in operation process,and puts forward optimization strategies for this technique,and hence,provides effective methods for separate-thin-layer and multi-stage fracturing treatment i tight sand,and shale reservoirs.