塔中超深碳酸盐岩储层水平井轨迹优化技术及应用

Optimization technology and application of horizontal well trajectory drilled in ultra-deep carbonate reservoirs in Tazhong area, Tarim Basin

塔里木盆地塔中凝析气田为超埋深(5000～7000m)复杂大型碳酸盐岩油气田,储层非均质性强,水平井水平段延伸长,纵向靶层识别难度大,导致水平井完井周期长和钻探成功率低,塔中气田稳产难度大。以往的碳酸盐岩储层水平井井眼轨迹设计,仅考虑了主应力方位,未考虑地应力综合特征,不能较好地保证水平井井眼钻遇优质储层发育带,无法优选有利于井壁稳定的井眼路径。以储层发育规律和储层地应力特征为基础,总结提出了储层钻遇率综合评价、储层顶面应力场预测和叠前叠后裂缝预测3项水平井轨迹优化技术。通过此3项技术的应用,水平井储层钻遇率明显上升,平均为46.5%,水平井钻井成功率在85%以上,实现了塔中气田的有效开发,同时为塔中地区及类似碳酸盐岩油气田的水平井井眼轨迹设计优化提供了依据和指导意见。

As an ultra-deep(5,000-7000 m), complex and large-scale carbonate oil and gas field, Tazhong-Ⅰ condensate gas field had heterogeneous reservoirs and difficulties in keep stable gas production because of long well completion period and low drilling success rate,which were caused by long horizontal sections and difficulties in identifying vertical target layers. Previous design of the wellbore trajectory of a horizontal well drilled in carbonate reservoirs only considered the principal stress, but not the comprehensive characteristics of geostress,so it could not ensure that the horizontal wellbore was drilled in good reservoir zones, accordingly it was hard to design a path favorable for wellbore stability. In this study, based on reservoir development law and geostress characteristics, three optimization techniques including comprehensive evaluation of reservoir drill-in rate, prediction of reservoir top stress field and pre & post-stack fracture prediction were proposed for optimizing horizontal well trajectory. Application of these three technologies has significantly increased the drill-in rate to an average of 46.5%, and the drilling success rate to over 85% in horizontal well development. This promoted the effective development of the Tazhong-Ⅰ gas field, and provided basis and support to the optimization design of horizontal wellbore trajectory for developing carbonate reservoirs in the Tazhong-Ⅰ gas field and other similar carbonate oil and gas fields.