老区直井重复体积压裂改造效果评价

doi:10.7657/XJPG20200319

摘要/Abstract

摘要：

借鉴于水平井体积压裂的理念,中国石油各大油田实施了直井重复体积压裂改造现场试验。老区直井地应力场较为复杂,且无法大规模运用微地震等监测技术评价压裂效果。基于试井数据、返排数据和生产数据,建立了压裂效果评价方法。评价模型考虑了地层真实非线性渗流,并用非线性因子与绝对渗透率的乘积表示地层的视渗透率,将储集层改造区域划分为不同复杂程度的次级裂缝区域,分析了次级裂缝区域分区在双对数曲线上的差异。算例敏感性分析可得出主裂缝缝长对生产阶段的后期影响较小,试井所得的主裂缝缝长可作为基本参数用于生产阶段拟合。以长庆油田老区直井为例,认为过早的关井测压会使测试结果不准确;老区直井重复体积压裂改造存在见水的风险;在返排和生产阶段,重复体积压裂改造效果逐渐变差,尤其核心区域变差的幅度更大,在生产阶段（150~246 d）,核心区域渗透率仅为返排阶段的13.3%,其改造区域面积仅为返排阶段的30.0%.

关键词: 老区, 直井, 储集层, 体积压裂, 非线性渗流, 数值试井

Abstract:

Based on the concepts of volume fracturing in horizontal wells, field tests of volume refracturing in vertical wells have been carried out in each oilfields of PetroChina. Because the geostress fields in vertical wells in existing blocks are complex and it is impossible to evaluate fracturing effect by using microseismic monitoring technique on a scale, this paper establishes a fracturing effect evaluation method based on well test data, flowback data and production data. The evaluation model proposed in this paper considers the true nonlinear flow in formations, and uses the product of nonlinear factor and absolute permeability to represent apparent formation permeability. The stimulated area can be classified into several secondary fracture areas according to fracture network complexity. The differences among different secondary areas on the double logarithmic curves are analyzed. Sensitivity analysis shows that the length of major fracture has a few impacts on later production, so that the major fracture length can be used as a basic parameter to do production match. Taking a vertical well in an existing block in Changqing oilfiled as a case, it is considered that premature shut-in pressure survey will result in deviations, there will be some risks of water breakthrough during volume refracturing in vertical wells. In the flowback and production stages, the effect of volume refracturing becomes poorer and poorer, which is more obvious in the core area. During the production stage, the permeability in the core area is only 13.3% of that in the flowback stage and the stimulated area in this stage is 30.0% of that in the flowback stage.

Key words: existing block, vertical well, reservoir, volume refracturing, nonlinear flow, numerical well test

中图分类号:

TE357.14

张安顺, 杨正明, 李晓山, 夏德斌, 张亚蒲, 赵新礼. 老区直井重复体积压裂改造效果评价[J]. 新疆石油地质, 2020, 41(3): 372-378.

ZHANG Anshun, YANG Zhengming, LI Xiaoshan, XIA Debin, ZHANG Yapu, ZHAO Xinli. Evaluation of Volume Refracturing Effect in Vertical Wells in Existing Blocks[J]. Xinjiang Petroleum Geology, 2020, 41(3): 372-378.

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