准噶尔盆地马桥凸起白垩系、侏罗系砂岩成岩演化机制与成岩模式

【作者】 夏显佰；

【导师】 施泽进； 陈布科；

【作者基本信息】 成都理工大学 ， 矿产普查与勘探， 2003， 博士

【摘要】 马桥凸起侏罗系和白垩系是准噶尔盆地油气勘探的重要层系，近几年已在该区发现了莫索湾大中型油气田和盆5井高产油气流。油气勘探的实践使石油地质学家认识到储层在油气成藏中的重要作用，芳2井钻探的失利更进一步意识到优质或相对优质砂岩储层的时空分布规律对指导油气勘探的重要意义。为此，需要研究马桥凸起侏罗系和白垩系砂岩储层的成岩-成孔演化机制，建立成岩模式。要研究的关键问题是储层的储集空间类型、储层的成岩机制和演化以及相对优质储层的分布规律。 本文从成岩物质和盆地动力作用两方面研究侏罗系和白垩系砂岩的成岩-成孔演化和成因机理，取得了以下主要认识： 1、侏罗系以原生孔隙型储层为主，是优质或相对优质储层的主要储集空间类型。其中，偏酸性成岩环境储层的溶孔较常见，可形成次生-原生孔隙型和原生-次生孔隙型储层。但其增孔作用小，尤其对渗透率的贡献更小。白垩系储层以原生孔隙为主。 2、侏罗系储层具有成分成熟度低、结构成熟度高和填隙物含量低的岩矿特征。它们是控制砂岩成岩作用和孔隙演化的内在因素，主要表现在砂岩的粒径和岩屑成分成熟度控制或影响了一定成岩环境中的水-岩反应速率、规模以及储层的抗压性和抗热性。由于该区的胶结作用弱，因此成岩物质对成岩作用的影响主要反映在成岩压实作用速率上，它产生的砂岩压实减孔量的差值可达5.5—6.0％。 3、控制砂岩成岩-成孔演化的盆地动力作用方面的因素很多，从其作用方式可分为垂向上的埋藏成岩作用和侧向上的构造挤压作用，在该区主要表现为第一种作用方式，并取决于该区的古地温场、地质作用时间、上覆负荷压力的作用方式(或储层热演化轨迹)和成岩水介质环境。在预测孔隙度时，前3个因素可用砂岩热成熟度参数定量表示之。(1)古地温场是决定砂岩成岩作用的关键因素。该区砂岩在深埋条件下仍处于较低成岩演化阶段和保存较高的孔隙度即与低古地温场有关;(2)地质作用时间和上覆负荷压力的作用方式对成岩压实作用也有明显影响，在今上覆负荷压力相同的情况下，白至系砂岩的压实程度明显小于侏罗系即主要与此因素有关;(3)偏酸性成岩环境砂岩具有快速压实阶段较早、颗粒溶蚀一压碎现象普遍而抗热性和抗压性差、自生矿物的自由生长空间较小以及储集性质较差等特点。它的化学成岩作用强于偏碱性成岩环境，并导致偏酸性成岩环境砂岩的化学一物理作用也大大加强，从而降低了砂岩的抗压性;(4)干早、半干早古气候是形成该区偏碱性成岩环境的先决条件，并造成碳酸盐和硬石膏的胶结作用较强;湿热气候是形成该区偏酸性成岩环境的先决条件，并造成高岭石的大量发育。 4、侏罗系、白蟹系砂岩的成岩模式有干早、半干早气候一偏碱性成岩水介质成因模式、湿热气候一偏酸性成岩水介质成因模式和湿热气候一中性成岩水介质成因模式等3大类。该区以前两种类型为主。 5、以粒径、塑性岩屑含量、成岩水介质和古地温场为4个成岩参量定t建立了砂岩储层的地质预测模型，结合测井定量预测模型，定量预测了储层的成岩演化速率和有利储层的分布，为油气勘探提供了靶区。其成果应用后已取得显著的经济效益。更多还原

【Abstract】 Jurassic and Cretaceous in Maqiao Salient is an important stratum of hydrocarbon exploration in Junggar Basin, where Mosuowan oil and gas field and high hydrocarbon output in Pen5 have been found in recent years.The hydrocarbon exploration in practice, especially the failure of Fang5 drilling makes petroleum geologists realize that reservoir is a very important factor for hydrocarbon trap, while space-time distributing regulation of high-quality or relative high-quality sandstone reservoir is instructive for hydrocarbon exploration. So it’s needed to work over the diagenetic and pore evolution mechanism of Jurrasic and Cretaceous sandstone in Maqiao Salient in order to establish diagenetic model, as a result ,to realize the type of reservoir space, the evolution of reservoir and the distribution of relative high-quality reservoir.This dissertation has studied the diagenetic and pore evolution regulation and genetic mechanism of Jurassic and Cretaceous sandstone in Maqiao Salient from the point of diagenetic mineral and basin dynamic function, and reached the following learnings:1. Jurassic sandsone reservoir is of primary pore type, which is the main type of relative high-quality reservoir space. Dissolved pore formed in acidic diagenetic enviroment is commonly observed in Jurassic sandstone. But corrosion to porosity enlarging is limited, and to permeability contribution is a little. Cretaceous sandstone reservoir is of primary pore type.2. Jurassic sandstone reservoir has such lithological characteristic as low compositional maturity, high textural maturity and low cenmentation content, which controls sandstone diagenesis and pore evolution. For instance, sandstone grain size and compositional maturity of debris controls water-rock reaction rate and scale, crushing resistance and heat resistance of reservoir. Because of low cementation, the influence of diagenetic mineral on diagenesis reflects on the ratio of diagenetic compaction. As a result of compaction,the porosity reducing in sandstone can reach to 5.5% to 6.0%.3. The burial diagenesis in vertical which is the main basin dynamic factor in Maqiao Salient and the tectonic compression in lateral are basin dynamic functions controlling sandstone diagenetic and pore evolution. The burial diagenesis are controlled by four parameters, i.e. paleogeotherm field, geological action time, loading pressure mode(or reservoir heat-evolution track) and diageneticwater-medium enviroment, and the first three parameters can be demonstrated quantificationally by heat maturity of sandstone to predict porosity. (1) Paleogeotherm field is the key factor for sandstone diagenesis. The low paleogeotherm field in Maqiao Salient determines sandstone in low diagenetic evolution phase and with high preserved porosity in such deep burial.(2) Geological action time and load pressure mode have a distinct effect on sandstone diagenetic compaction. For example, with the same overlying load pressure, compaction degree of Cretaceous is oboviously less than that of Jurassic. (3) Sandstone in acidic diagenetic enviroment has such characteristic as fast compaction rate, earlier compaction stage, prevalent grain solution and crushing, poor heat resistance and crushing resistance, small free growing space of authigenic mineral, poor reservoir properties and so on. It has undergone stronger chemical diagenesis than in alkaline diagenetic enviroment. Furthermore, its chemical-to-physical reaction is more active. So its crushing resistance is reduced. (4) Alkaline diagenetic enviroment in Maqiao Salient formed in arid climate or semiarid climate, and resulted in the cementation of carbonate and anhydrite. But acidic diagenetic enviroment formed in humid climate, and resulted in the growth of kaolinite.4. There are three types of diagenetic model in Jurassic and Cretaceous sandstone, namely arid or semiarid climate-diagenetic alkaline water medium genetic model, humid climate- diagenetic alkaline water medium genetic model and humid climate- diagenetic neutral water更多还原