塔里木盆地古城地区奥陶系天然气勘探重大突破及其启示

Ordovician gas exploration breakthrough in the Gucheng lower uplift of the Tarim Basin and its enlightenment

2012年位于塔里木盆地古城低凸起上的古城6井奥陶系获高产稳产天然气流,发现了塔里木盆地继塔中、塔北之后的又一个碳酸盐岩增储上产领域。古城低凸起的勘探经历了由海相碎屑岩勘探向奥陶系坡折带台缘礁滩体勘探,再向奥陶系台内层间岩溶领域勘探的3个阶段:①1995—2003年,以东河砂岩海湾岩性圈闭、志留系超覆岩性圈闭与上奥陶统浊流沉积体为主要目标的海相碎屑岩勘探阶段;②2003—2006年,以坡折带台缘礁滩体为主要目标的勘探阶段,古城4井见到了油气发现的曙光;③2007—2009年深化了层间岩溶勘探认识,突出地震攻关,优选有利区带,打破常规超前部署三维地震为油气突破奠定了重要基础,2009—2012年,精细研究,部署古城6井,取得了油气勘探的重大突破。古城6井的重大突破,证实了古城地区下古生界碳酸盐岩地质条件优越,油气勘探前景广阔,为油气勘探带来了3点重要启示:①地质认识的突破,是获得勘探突破的前提;②攻克瓶颈技术,部署三维地震,是获得勘探突破的重要保障;③解放思想、坚持探索是实现新区勘探突破的关键。

A steady high yield natural gas flow was discovered in the Ordovician strata in 2012 when Well Gucheng-6 was drilled in the Gucheng lower uplift in the Tarim Basin, so another carbonate gas exploration field has been discovered after the other two fields in the middle and northern Tarim Basin （the so-called Tazhong and Tabei within the industry）. The exploration in the Gucheng lower uplift has experienced the following stages： at the first stage of the marine facies clastic exploration process during 1995 - 2003, the Devonian Donghe sandstone lithologie trap, the Silurian overlapping lithologic trap, and the Upper Ordovician shelf slope turbidites were taken as three main targets; at the second stage of the reef-shoal carbonate reservoir exploration process during 2003 2006, oil and gas were first discovered in Well Gucheng-4 as a twilight; at the third stage of the interbedded karstification reservoir exploration process, a robust foundation was laid for the subsequent great discovery by focusing on seismic techniques, optimizing favorable zones, and breaking all rules to advance the 3D seismic deployment; and during 2009 - 2012, through an in-depth investigation, Well Gucheng-6 was drilled and completed with great breakthrough in oil and gas exploration in this study area. This success proves that there are satisfactory geological conditions in the Lower Paleozoic carbonate rocks in the Gucheng area with a great prospect of oil and gas exploration. From this success we can also learn three important things： it is a premise to have a better geological under- standing; it is a guarantee to solve those bottlenecking problems and advance 3D seismic deployment; and it is a key to success for us to free our minds and persevere in exploration.