鄂尔多斯盆地页岩油水平井开发关键科技问题

Key scientific and technological issues in the development of horizontal shale oil wells in the Ordos Basin

中国石油长庆油田分公司以鄂尔多斯盆地三叠系延长组7段(长7段)富有机质泥页岩层系中的重力流砂岩薄夹层为目标,实现了陆相低压淡水湖盆夹层型页岩油的规模效益开发,发现并探明了10亿吨级庆城页岩油大油田,累计提交探明储量10.52×10^(8)t,率先建成了中国第一个百万吨页岩油整装开发区。随着产建规模不断扩大,地质体差异明显,单井初期产量低且递减快、采收率低、开发成本高等问题越来越突出。通过多年的矿场实践,提出了页岩油开发中的关键科技问题,并根据系统分析提出了合理建议。页岩油水平井钻遇率可分为纵向钻遇率及横向钻遇率,提高优质储层纵向、横向钻遇率是提高单井产量的重要举措;水平井部署时可优先考虑优质储层的延伸方向,提高优质储层的钻遇率;压裂液弹性能对采收率贡献占比相对较低,储层改造不能过度强调大砂量、大液量、大排量,要充分考虑井距、纵向隔夹层分布、裂缝发育情况,优化压裂规模、施工排量等参数;烃源岩品质变化和成岩作用的强弱是造成砂体含油性差异的主要原因,影响有利区选取及优质储层分布;前置CO_(2)增能体积压裂增能效果明显,是降黏提高采收率的有效手段。深化地质综合研究,明确页岩油差异成藏主控因素、精细刻画三维甜点展布、探索更加有效的开发方式,是保障长庆油田页岩油高效开发的重要举措。

Aiming at the thin interbeds of gravity flow sandstone in organic-rich shale layer of the 7th member of Triassic Yanchang Formation(Chang7 Member)in Ordos Basin,PetroChina Changqing Oilfield Company realized the cost-effective development of interbedded shale oil in continental low-pressure freshwater lacustrine basin,discovered and proved the 1 billion ton Qingcheng shale oil field,and presented proven reserves of 10.52×10^(8)t.It took the lead in building China's first one million ton shale oil integrated development zone.With the continuous expansion of production and construction scale,the difference of geological body is obvious,and the problems of low initial production and rapid decline of single well,low recovery efficiency and high development cost become more and more prominent.Through many years of field practice,the key problems in shale oil development are put forward,and reasonable suggestions are put forward according to systematic analysis.The drilling rate of shale oil horizontal wells can be divided into longitudinal drilling rate and transverse drilling rate.Improving the longitudinal drilling rate and transverse drilling rate of high-quality reservoir is an important measure to increase the production of a single well.When deploying horizontal wells,priority can be given to the extension direction of high-quality reservoirs to improve the drilling rate of high-quality reservoirs.The contribution ratio of elastic energy of fracturing fluid to recovery is relatively low,so the reservoir reconstruction should not overemphasize large sand volume,large fluid volume,and large displacement,but should fully consider well spacing,longitudinal interlayer distribution,and fracture development,and optimize fracturing scale,construction displacement and other parameters.The change of source rock quality and the strength of diagenesis are the main reasons for the difference of oil content in sand bodies,which affect the selection of favorable areas and the distribution of high-quality reservoirs.Pre-CO_(2)volumetric fracturing has obvious energy increase effect,which is an effective means to reduce viscosity and improve oil recovery.It is an important measure to ensure the efficient development of shale oil in Changqing Oilfield Company by deepening the comprehensive geological research,clarifying the main controlling factors of differential shale oil accumulation,elaborating the three-dimensional sweet spot distribution,and exploring more effective development methods.