A Successful Seismic Integration Case in Exploration of the Deep Thrust Zone in Mountain Area of Qaidam Basin, West China

Abstract

The western Yingxiongling Mountain in Qaidam Basin of China has very attractive hydrocarbon potential in deep section, but the rough plateau condition and complex geology present the major challenges in deep exploration. Early deep drilling without seismic in 1980s had resulted in about 20 dry holes and two discoveries, which led to a total 2 million bbl of oil production from 4 wells. To improve the operation, 3D seismic was acquainted in 2013. With this dataset, Schlumberger has performed an integrated geophysical study with PSDM processing and seismic interpretation. As the study result, two wells have been put in drilling in late 2014. The first well tested over 1000 bbl/day and was put in production. The second well has penetrated 80m pay-zones and will be tested in coming spring. This success has led to a breakthrough in deep exploration and production in this mountainous area. The workflow of our study include: (1) Establishing a set of practical processing technologies for low signal/noise ratio, complex mountain area: integrated statics, combined noise attenuation, robust surface consistent deconvolution, and providing high quality dataset for subsequent imaging; (2) Enhancing imaging quality especially for over-thrust and underneath: a proper strategy with well-constrain for velocity model building that leads to improved depth imaging results and good consistency with geological markers; Reverse time migration significantly improved imaging quality for underneath over-thrust which provide reliable stratigraphic contact and reasonable structure distribution. (3) Setting up proper regional structural -stratigraphic framework: low-angle imbricate thrust faults with associated multi-level decollement folds, which lays down the sound basis for further reservoir analysis. (4) Comprehending the main control factor on deep reservoir: the alignment of big thrust faults with lithology rich in brittle and soluble dolomite/ limestone determines the sweet-spots with rich oil accumulation and high production. (5) Taking the understanding of reservoir as the guidance and two old production locations as starting points, four favorable zones are delineated for scrolling drilling deployment. In contrast to our successful integrated seismic study, a parallel seismic study by another company has applied structural trapping and seismic attribute analysis in PSTM dataset as guidance in prospect generation and drilling location delineation, which has led to 4 dry holes till now.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015