AN区块致密油藏低产水平井裂缝诊断方法

Fracture diagnosis method for low-yield horizontal well in tight oil reservoir of AN block

常规测试技术难以评价鄂尔多斯盆地AN区块致密油藏低产水平井长期生产状态下的各段裂缝状况。为准确掌握低产水平井措施前各段裂缝关键信息,设计了压缩式双封单卡管柱,获取水平井分段变排量挤注压力和关井后压降数据,应用裂缝挤注指示曲线、瞬时停泵压力和裂缝扩散压力综合评价水平井初次改造充分性、射孔孔眼堵塞情况,并求取水平井分段油藏压力和产量。在AN区块致密油藏水平井开展了测试及分析,结果表明该裂缝诊断方法可判识分段裂缝的初次改造程度、孔眼堵塞情况,且3种油藏压力分析方法计算结果基本一致,可相互验证。诊断结果为措施潜力井段筛选、工艺优选及参数优化提供指导。对开展了诊断测试的4口致密油藏低产水平井实施重复改造,与未测试的措施水平井相比单井产量提高了70%。该方法对其他非常规储层低产水平井措施前的裂缝诊断具有一定的借鉴意义。

In the AN block of the Ordos Basin, the long-term fracture creation in low-yield horizontal wells in tight oil reservoir can not be effectively evaluated by conventional testing techniques. In order to accurately learn the key information of fractures before stimu-lation in low-yield horizontal wells, the compression type double-sealing ＆ single-stick string was designed to obtain the sectional vari-able displacement squeeze pressure and shut-in drawdown data of horizontal wells. Then, fracture squeeze index curve, instantaneous pump off pressure and fracture diffusion pressure were used to conduct integrated evaluation on the primary reformation suffciency and perforation blockage situations of horizontal wells, and thus obtain the sectional reservoir pressure and output of horizontal wells. Test and analysis were conducted in horizontal wells in tight oil reservoir, the AN block, showing that this fracture diagnosis method can be used to discriminate the primary reformation level of sectional fractures and the perforation blockage situations. Furthermore, the calculation results of the 3 kinds of reservoir pressure analysis methods are basically the same, which can be mutually verifed. The diagnostic results have provided directions for the screening of potential stimulation section, the technology optimization and the pa-rameter optimization. Repeated stimulation was implemented in 4 low-yield horizontal wells in tight oil reservoir, where diagnostic test had been carried out, and the single well output was increased by 70% than the stimulated horizontal well that had not been tested. This method can provide reference to the pre-stimulation fracture diagnosis of low-yield horizontal wells in other unconventional reservoirs.