Petroleum Geology in the Tarim，Junggar and Turpan－Hami Basins Showing Favorable Conditions for the OccurrenceofLargeandMediumoilandGasFields

The frequent upwarping and subsidence,and folding and uplifting of the earth crust caused by the isostatic adjustments and tectonic movements change the types of sediments in the basins frequently,and often cause the occurrence of multi-source formations in the geologic profile.As in the Tarim basin,during the first transgression in the early paleozoic,the deepest location was the Ordovician sag,in which deep marine clastic and carbonate rocks were deposited and main source rocks were included.In the late Paleozoic,it was the second transgression cycle,the thickest sedi-ments of Carboniferous-Permian were deposited in thie Awati sag and southwest sag which would be another major petroleum source rocks(Fig.2).

Geological characteristics of large gas provinces and large gas fields in China

Based on the examination of the global researches on oil and gas provinces and large gas fields and the analysis of the features,attributes and distribution of large gas provinces and gas fields,this paper puts forward three indicators of determining large oil and gas provinces:spatial indicator,reservoir-forming indicator and resource indicator.It classifies the gas accumulated areas and large gas provinces in China and analyzes the controlling factors on the distribution of large gas provinces and large gas fields:the lateral distribution is mainly controlled by high-energy sedimentary facies and constructive diagenetic facies,palaeo-highs and their periclinal zones,deep faults,etc,and the vertical distribution is mainly controlled by unconformities,series of evaporates and deep low-velocity highly-conductive beds,etc.It also reveals the main geological characteristics of large gas provinces and large gas fields in China.Large gas fields in four-type basins have their own characteristics and onland large gas fields are dominantly developed in foreland basins and craton basins;there are three types of gas sources,of which,coal is the main source with high gas generating intensity and varying origins;reservoir rocks of the large gas fields(provinces)are of various types and dominated generally by low-middle permeability and porosity pore-type reservoirs;structural traps and litho-stratigraphic traps coexist in Chinese large gas fields and form dense high abundance and large-area low and middle-abundance large gas fields;most of the large gas fields have late hydrocarbon-generation peaks and reservoir formation,and experienced the process of multiple-stage charging and late finalization; large gas provinces(fields)have good sealing and preservation conditions,and evaporates seals are largely developed in large and extra-large gas fields.This paper intends to shed light on the exploration and development of large gas fields(provinces)through analyzing their geological characteristics.

油气藏型储气库地质体完整性内涵与评价技术

地下储气库(以下简称储气库)全生命周期完整性管理已成为其长期安全有效运行的重要保障,目前我国油气藏型储气库完整性及其评价技术以地面设施和注采井为主,地质完整性评价对象与概念不明确且缺乏系统的评价技术。为此,在总结相关研究成果的基础上,提出了以储气地质体为评价对象的地质体完整性概念,建立了油气藏型储气库地质体完整性评价技术体系,并以新疆呼图壁储气库为实例开展了储气库地质体完整性评价。研究结果表明:①储气库地质体完整性是指在储气库运行过程中,储气地质体各组成部分能够满足运行要求、安全经济地完成季节与应急调峰任务的各项性能指标的完整程度,其内涵是在储气库运行生命周期内,地质体的储层以及盖层、断层和圈闭可以为用户持续稳定提供气量,并保证储气库安全运行,其核心是在储气库运行生命周期内保持天然气存储的可靠性、安全性和经济性的程度;②地质体完整性评价技术体系由圈闭有效性、盖层完整性、断层稳定性、储层稳定性4项评价技术构成;③评价结果显示,呼图壁储气库具有提高上限压力扩大调峰气量的潜力。结论认为,油气藏型储气库地质体完整性评价技术体系的建立,健全了储气库完整性评价技术系列,对油气藏型储气库长期安全有效运行、提高运行上限压力、增强调峰能力等具有指导作用和应用价值。

微地震监测在油气藏型储气库地质体完整性评价中的应用

油气藏型储气库是利用枯竭油气藏改建而成的地下储气空间,是最主要储气库类型。与国外油气藏型储气库相比,中国储气库地质体大多为复杂断块,具有埋藏深、储层渗透性差、非均质性强等特点。中国独特的复杂地质条件给储气库地质体安全运行带来巨大挑战,微地震监测技术可实时监测地层岩石破裂情况,是储气库地质体活动最直接的监测手段。为此,从微地震监测原理及储气库地质体完整性定义出发,针对储气库微地震监测数据特点对数据处理方法进行研究,并以新疆呼图壁储气库为例,开展微地震监测数据处理、解释,对呼图壁储气库地质体完整性进行评价。结果表明:①微地震监测技术在保障储气库地质体安全中具有重要作用,可实时监测断层、盖层、底层等岩石破裂活动;②在研究期内呼图壁储气库地质体较稳定,储层深度附近并未发生微地震事件明显聚集、大震级微地震事件等现象,但仍需长期监测;③可实现三维立体微地震监测,相比于常规方法,其监测范围更广、监测信息更丰富。