岩相古地理研究可作为页岩气地质调查之指南

得益于水平井和压裂技术的发展,页岩气已成为中国油气勘探开发的热点。沉积环境决定了有机质的含量、类型、矿物组成和含量、厚度、埋深等页岩气基本地质要素的特征。在开展区域沉积相研究的基础上,通过岩相古地理编图方法,可以明确烃源岩有利相带的时空分布,从而为页岩气勘探提供基础和方向。以四川盆地南部及邻区志留系龙马溪组为例,通过详细的沉积相及岩相古地理研究,确定了烃源岩的有利相带和空间展布特征。在岩相古地理图的基础上,叠加矿物组成、有机碳含量、成熟度、厚度等页岩气评价参数,预测了四川盆地南部及邻区志留系龙马溪组页岩气远景区和有利区。页岩气地质调查的根本目标是寻找页岩气的远景区和有利区,为页岩气勘探开发提供科学依据。因此,岩相古地理研究与编图可作为基本方法及关键的技术,为页岩气的地质调查工作提供指南。

A study of lithofacies-palaeogeography as a guide to geological survey of shale gas

Benefited from the development of horizontal well and the fracturing technology, shale gas has become a hot field in oil and gas exploration and development in China. Sedimentary environment determines the characteristics of basic geology elements of shale gas, such as the organic carbon content and type, mineral composition and content, thickness and the buried depth of hydrocarbon source rocks. On the basis of the study of the regional sedimentary facies, according to the litheofacies palaeogeographic mapping, it can explicit the spatio-temporal distribution of favorable facies belt of the hydrocarbon source rocks, which can provide the basic direction of the shale gas exploration. A case study of shale gas geological survey work on Longmaxi Formation in Southern of Sichuan Basin and its periphery was carried out, it can confirm favorable facies belt and the characters of the roomage distribution of hydrocarbon source rocks. Based on the litheofacies palaeogeographic, through superimpose the composition of the mineral, organic carbon content, maturity and the thickness, which are the evaluation parameters of shale gas, it can forecast the prospects and favorable area of shale gas on Longmaxi Formation in Southern of Sichuan Basin and its periphery. The fundamental target of geological survey work about shale gas is to find the prospects and favorable area, which can provide scientific basis for shale gas exploration and development. As a result, the study of lithofacies palaeogeography can be a guide for geology survey of shale gas.