Seismic exploration techniques and effects in Lunnan Buried Hill

摘要

Lunnan Buried hill is located in Lunnan low convex of middle Tabei uplift of Tarim Basin, and it is a Paleozoic residual paleohigh. The buried-hill stratum is mega-thick carbonates of middle-and-lower Ordovician. Most of its overburden layer is Carboniferous mudstone, and in some local high position it is Triassic sandstone. The buried-hill structure as a whole is a giant anticline with the area of about 2400 square kilometers. On this anticline, there developed two rows of horsts, including Lunnan horst and Sangtamu horst, and four slopes. They are the northern, middle, south-Sangtamu and western slopes. The buried hill was found by using 2D seismic exploration in 1986, and high yield hydrocarbon was obtained in 1988. In the following ten years, 2D and 3D seismic exploration as well as drillings had been carried out on a large scale, and 52 wells had been drilled till 1988. It is the most important hydrocarbon exploration area in Ordovician carbonates of Tarim basin. Because the surface and underground geological structure is very complicated, the average groundmass porosity is less than 2%, the main reservoir space is dissolved fractures and caverns, the reservoir itself is highly anisotropic, and its buried depth is more than 5100 to 5800 meters, etc., on the background that the buried hill is hydrocarbon bearing at large, the rate of successful drilling was less than 20%, which seriously restrict the progress of petroleum exploration and development (E&D). Only in recent three years, by tackling the key exploration project of acquisition-processing-interpretation integration (APII) with high-resolution (HR) 3D seismic data, the real exploration breakthrough was reached.