苏丹福拉凹陷陡坡带构造地质特征及勘探

Tectonic geology and exploration in the western escarpment of Fula sub-basin,Sudan

福拉凹陷区域地质上属于在中非剪切带应力场背景下拉张形成的被动裂谷凹陷,整体呈西断东超的箕状凹陷,西部陡坡带为一个受长期活动的边界断层控制的一个狭长区域,面积约400 km2。该构造带具有构造复杂,地层产状陡,沉积相变化快等特点,因而在地震采集和处理技术、石油地质综合评价和钻井作业技术方面面临一系列挑战。综合地质研究及勘探实践证实,对于复杂断块油气田,及早部署三维地震采集以落实复杂构造并采用滚动勘探开发的思路,可以快速、有效地探明储量规模,减少失误,提高勘探效益;针对不同的地下及地表条件,优化采集参数和接收组合,并在构造主体部位采用加密炮线增加局部覆盖次数,有利于改善地震资料品质;适时调整钻井工程技术,可有效地提高钻探效率和井身质量,有利于油层的发现和储集层保护。

Fula sub-basin is a passive rift sag formed by the extensional stress resulted from Central Africa Shear Zone. It is an asymmetric half-grahen, which develops fault steps to the west and is overlapped to the east. The western escarpment is a long and narrow structure of about 400 km^2 , controlled by a long-lived boundary fault. Due to complicated structure, steep stratum and varied sedimentary facies, there are many challenges for exploration in the escarpment, such as the seismic data acquisition and processing, integrated G＆G study, drilling technology, etc. The integrated G＆G study and exploration practice proved that the strategy of early deployment of 3D seismic acquisition and applying progressive exploration and development can efficiently decide reserves, reduce risks and enhance exploration benefits. Optimizing the seismic acquisition parameters and infilling shot points to improve the local fold times in the main part of the structure according to the conditions of subsurface and surface is beneficial to enhancing the seismic data quality. Timely adjusting the drilling technology can improve the drilling efficiency and the quality of borehole condition, which is helpful to discover pay zones and protect reservoirs.