大宁–吉县区块深层煤层气井酸压工艺及现场试验

Acid fracturing technology of deep CBM wells and its field test in Daning-Jixian Block

我国深层煤层气资源储量丰富,但煤储层改造工艺技术与深层地质条件匹配耦合性问题亟需解决。为探究深层地质条件下煤储层改造技术,以大宁–吉县区块为地质背景,从该区块深层8号煤层岩石力学参数角度对体积压裂可行性进行评价,并采用室内三轴酸压物模实验进行验证。基于室内实验的基础上,针对此区块8号煤层特征,提出采用“高排量、低酸量、适中砂比”体积酸压工艺技术,并配合“交替注酸、分段加砂、变排量注入”复合工艺。基于此工艺原理开展复合盐酸、氨基磺酸体积压裂现场试验。结果表明:现场11口产气井日产气量累计达20469 m^(3),其中10口生产直井最高产气量可达5791 m^(3)/d;1口生产水平井投产后日产气最高1.1万m^(3),同时体积酸压工程因素(排量、加液强度)与裂缝监测破裂面积存在较好相关性。提出应进一步提升压裂液排量且应优选在11~15 m^(3)/min;应减小整体用酸量,同时进一步优选酸液浓度;优选低密度支撑剂并优化加砂工艺以提升加砂规模;清洁压裂液加液强度优选在150~250 m^(3)/m;同时应提升配套设备质量,例如提升套管钢级,优化压裂设备等。研究从体积酸化压裂工程角度为该区块及类似地质条件下深层煤层气的勘探开发提供了技术借鉴。

There are abundant deep coalbed methane resources in China,but the coupling problem of coal reservoir reconstruction technology and deep geological quality conditions needs to be solved urgently.With Daning-Jixian Block as the geological background,the feasibility of volumetric fracturing is evaluated from the perspective of rock mechanical parameters of the No.8 coal seam in a deep layer of the block,and verified by the indoor triaxial acid fracturing model experiment,in order to explore the coal reservoir reconstruction technology under deep geological conditions.Based on the above basic research,the volume acid fracturing technology characterized by high displacement,low acid dosage,and the moderate sand ratio is proposed for the No.8 coal seam in this block with the composite technology featured by alternating acid injection,subsection sand addition,and variable rate injection.Field tests of complex hydrochloric acid and sulfamic acid volume fracturing are carried out based on this process principle.The results show that the accumulative daily production of 11 gas-producing wells reaches 20469 m^(3),among which the maximum gas production of 10 vertical production wells reaches 5791 m^(3)/d.One horizontal production well has a maximum daily gas production of11000 m^(3).At the same time,there is a good correlation between the volume acid fracturing engineering factors(displacement,fluid intensity)and the monitored fracture area.It is suggested that the fracturing fluid flow rate should be further increased,and the optimal fracturing fluid flow rate 11-15 m^(3)/min.The overall acid content should be reduced and the acid concentration should be further optimized.The low-density proppant is selected and the sand adding process is optimized to increase the sand adding scale.Clean fracturing fluids should preferably be added at a strength of150-250 m^(3)/m.At the same time,the quality of supporting equipment should be improved,such as upgrading casing steel grades and optimizing fracturing equipment.This study provides a technical reference for the exploration and development of deep coalbed methane in this block or under similar geological conditions from the perspective of volume acidizing fracturing engineering.