非常规油气藏形成机理及开发关键技术
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摘要
随着世界对天然气资源需求的不断增加以及常规天然气储量的日益减少，很多国家都将致密砂岩气藏作为重要的后备资源，在一些国家已进行了大规模的勘探开发，并获得了可观的经济和社会效益。据全国第二轮资源评价结果，我国陆上天然气资源为30.23×10~(12)m~3，其中非常规致密天然气资源占其中40％左右(约12×10~(12)m~3)，目前我国天然气产量中有近1／3产自非常规的致密碎屑岩储层。按我国现有的油气储量分析，到2010年左右，我国的常规天然气高峰即将过去，必须有新的后备资源补充，因此非常规致密气资源将是主要的接替能源。
川西坳陷上三叠统致密碎屑岩含气领域是四川盆地重要的天然气能源生产基地，天然气资源量达18000～25000×10~8m~3，资源十分丰富。但目前所获天然气探明加控制储量2300×10~8m~3，仅占总资源的10.7％，勘探开发潜力巨大。通过川西坳陷上三叠统成藏机理、天然气富集规律、致密低渗透气藏预测技术、开发技术等综合研究，本论文在如下方面取得了创新性成果：
1．世界主要含油气区，油气藏形成条件及全过程往往完成于一个重要构造期内，对于多旋回叠合盆地，跨越若干重大构造期油气藏形成的理论研究仍是现今世界上急需解决的难题。川西坳陷自晚三叠世以来，经历了多期构造运动，导致了上三叠统须家河组岩石物性、构造特征、流体性质和地压场的多期次变化，油气运移聚集经多次反复而成藏。通过对上三叠统天然气成藏机制和天然气分布规律的研究，认为早期“古构造”是天然气藏形成的基础，中期致密化“封存”是天然气保存的条件，晚期“裂缝活化”是天然气富集的关键。首次提出了“早聚、中封、晚活化”致密碎屑岩递进动态成藏地质机理，解决了川西坳陷这个跨越若干重大构造运动时期及深层—超深层领域的油气成藏理论问题，丰富和发展了天然气成藏地质理论。
2．通过开展川西坳陷上三叠统生排烃高峰、储层致密化进程、裂缝形成期和圈闭形成期及其时空配置的研究，解决了上三叠统超深超压领域成藏年代学问题。明确了须家河组二段的充注高峰在须四末—中侏罗世末；须四段的充注高峰在晚侏罗世—晚白垩世。
3．在认真总结勘探经验和深入研究天然气成藏机制的基础上，明确指出了川西坳陷上三叠统天然气的富集规律是：天然气区域成矿带位于大型古隆起和斜坡区；天然气的聚集类型以构造、地层和岩性圈闭为主；天然气高产富集部位是叠加在有效圈闭上的天然显裂缝系统。为油气勘探部署指明了方向。
4．开发形成了深层超致密储层的天然气富集带综合预测技术、裂缝性储层识别和含气性预测地球物理方法技术。
5．配套完善了深层超致密气藏包括产能评价、井网优化、控水排水、储层改造、钻完井及储层保护的开发关键技术系列。
With the increasingly demand of natural gas & decreasingly supply of natural gas reserve in the world, the tight sandstone gas reservoir has been taken as the important reserve resource by many countries, most of which have explored and developed in large scale and achieved economic & social benefits. From the results of the second round resource evaluation, our national onshore natural gas is 30.23 × 10~(12) m~3, some of which are from abnormal tight natural gas with about 40% of total ( about12×10~(12) m~3 ). At present, nearly 1/3 natural gas production is produced from abnormal tight classic reservoir. Our current reserve analysis shows that the normal natural gas peak point will be dropped down by 2010, it must have new takeover resource for supplement. So, abnormal tight natural gas resource shall be an important takeover energy. Upper Triassic tight classic natural gas in western Sichuan basin is an important natural gas energy production base with 18000 - 25000×10~8m~3 in Sichuan basin. But it still has potential exploration & development future due to 2300×108 m~3 proved & probe reserve with only 10.7% of total energy. Through the research of reservoir forming mechanism, rules of enrichment, prediction technology for tight low permeability and development technologies, this article achieves the following innovative results.
1. The conditions and whole process of main gas-bearing areas in the world are generally completed in an important tectonic event. But for the multi cycle superimposed basin, it is still a problem to be solved for the theoretical study of reservoir forming with several important tectonic events. The several tectonic events of western Sichuan depression since late Triassic leads to the changes of physical property, structure characteristics, fluid characters and stress field of upper Triassic Xujiahe formation, and the migration & accumulation of oil & gas formed after going through many times. Based on the research of reservoir forming mechanism, rules of enrichment, it is considered that the early palaeostructure is the basis of gas accumulation in early period, abnormal overpressure compartment is condition of natural gas preservation in middle period, fracture activation is the key point of natural gas enrichment in late period, so it is put forward the progressive dynamic geologic theory of tight classic rock in western Sichuan, that is "early accumulation, middle compartment and late activation", and solves the oil & gas reservoir theoretic problem of undergoing several important tectonic events and deep—super deep formation in western Sichuan depression, meanwhile, it riches and expands the geologic theory of reservoir forming.
2. Through the research for hydrocarbon generating & expulsion peak point, reservoir tightening, fracture forming & trap forming period and its time—space disposition, it solves the chronology problem of upper Triassic super deep & over pressure and makes it clear that the fill peak of 2~(nd) section of Xujiahe formation is at late Xu~4—late middle Jurassic, the filling peak of Xu~4 is at late Jurassic -late Cretaceous.
3. On the basis of exploration & development experiences and further research of reservoir forming mechanism, it is pointed the enrichment rules of upper Triassic natural gas is that natural gas regional mineralizing belt located at large scale paleohigh & slope, the types of accumulation is mostly structural, stratigraphic and lithologic traps, high production place is at clear natural fracture systems stacked at effective traps, all which point out the direction of exploration
4. The comprehensive prediction technology for natural gas enrichment belt of super tight reservoir in deep formation, the recognition technology for fractural reservoir and gas prediction geophysical method & technology have been developed and formed.
5. Some key technologies of productivity evaluation, well net optimization, water controlling & discharge and reservoir modification, drilling, completion and reservoir protection have been improved & perfected.
川西坳陷上三叠统致密碎屑岩含气领域是四川盆地重要的天然气能源生产基地，天然气资源量达18000～25000×10~8m~3，资源十分丰富。但目前所获天然气探明加控制储量2300×10~8m~3，仅占总资源的10.7％，勘探开发潜力巨大。通过川西坳陷上三叠统成藏机理、天然气富集规律、致密低渗透气藏预测技术、开发技术等综合研究，本论文在如下方面取得了创新性成果：
1．世界主要含油气区，油气藏形成条件及全过程往往完成于一个重要构造期内，对于多旋回叠合盆地，跨越若干重大构造期油气藏形成的理论研究仍是现今世界上急需解决的难题。川西坳陷自晚三叠世以来，经历了多期构造运动，导致了上三叠统须家河组岩石物性、构造特征、流体性质和地压场的多期次变化，油气运移聚集经多次反复而成藏。通过对上三叠统天然气成藏机制和天然气分布规律的研究，认为早期“古构造”是天然气藏形成的基础，中期致密化“封存”是天然气保存的条件，晚期“裂缝活化”是天然气富集的关键。首次提出了“早聚、中封、晚活化”致密碎屑岩递进动态成藏地质机理，解决了川西坳陷这个跨越若干重大构造运动时期及深层—超深层领域的油气成藏理论问题，丰富和发展了天然气成藏地质理论。
2．通过开展川西坳陷上三叠统生排烃高峰、储层致密化进程、裂缝形成期和圈闭形成期及其时空配置的研究，解决了上三叠统超深超压领域成藏年代学问题。明确了须家河组二段的充注高峰在须四末—中侏罗世末；须四段的充注高峰在晚侏罗世—晚白垩世。
3．在认真总结勘探经验和深入研究天然气成藏机制的基础上，明确指出了川西坳陷上三叠统天然气的富集规律是：天然气区域成矿带位于大型古隆起和斜坡区；天然气的聚集类型以构造、地层和岩性圈闭为主；天然气高产富集部位是叠加在有效圈闭上的天然显裂缝系统。为油气勘探部署指明了方向。
4．开发形成了深层超致密储层的天然气富集带综合预测技术、裂缝性储层识别和含气性预测地球物理方法技术。
5．配套完善了深层超致密气藏包括产能评价、井网优化、控水排水、储层改造、钻完井及储层保护的开发关键技术系列。
With the increasingly demand of natural gas & decreasingly supply of natural gas reserve in the world, the tight sandstone gas reservoir has been taken as the important reserve resource by many countries, most of which have explored and developed in large scale and achieved economic & social benefits. From the results of the second round resource evaluation, our national onshore natural gas is 30.23 × 10~(12) m~3, some of which are from abnormal tight natural gas with about 40% of total ( about12×10~(12) m~3 ). At present, nearly 1/3 natural gas production is produced from abnormal tight classic reservoir. Our current reserve analysis shows that the normal natural gas peak point will be dropped down by 2010, it must have new takeover resource for supplement. So, abnormal tight natural gas resource shall be an important takeover energy. Upper Triassic tight classic natural gas in western Sichuan basin is an important natural gas energy production base with 18000 - 25000×10~8m~3 in Sichuan basin. But it still has potential exploration & development future due to 2300×108 m~3 proved & probe reserve with only 10.7% of total energy. Through the research of reservoir forming mechanism, rules of enrichment, prediction technology for tight low permeability and development technologies, this article achieves the following innovative results.
1. The conditions and whole process of main gas-bearing areas in the world are generally completed in an important tectonic event. But for the multi cycle superimposed basin, it is still a problem to be solved for the theoretical study of reservoir forming with several important tectonic events. The several tectonic events of western Sichuan depression since late Triassic leads to the changes of physical property, structure characteristics, fluid characters and stress field of upper Triassic Xujiahe formation, and the migration & accumulation of oil & gas formed after going through many times. Based on the research of reservoir forming mechanism, rules of enrichment, it is considered that the early palaeostructure is the basis of gas accumulation in early period, abnormal overpressure compartment is condition of natural gas preservation in middle period, fracture activation is the key point of natural gas enrichment in late period, so it is put forward the progressive dynamic geologic theory of tight classic rock in western Sichuan, that is "early accumulation, middle compartment and late activation", and solves the oil & gas reservoir theoretic problem of undergoing several important tectonic events and deep—super deep formation in western Sichuan depression, meanwhile, it riches and expands the geologic theory of reservoir forming.
2. Through the research for hydrocarbon generating & expulsion peak point, reservoir tightening, fracture forming & trap forming period and its time—space disposition, it solves the chronology problem of upper Triassic super deep & over pressure and makes it clear that the fill peak of 2~(nd) section of Xujiahe formation is at late Xu~4—late middle Jurassic, the filling peak of Xu~4 is at late Jurassic -late Cretaceous.
3. On the basis of exploration & development experiences and further research of reservoir forming mechanism, it is pointed the enrichment rules of upper Triassic natural gas is that natural gas regional mineralizing belt located at large scale paleohigh & slope, the types of accumulation is mostly structural, stratigraphic and lithologic traps, high production place is at clear natural fracture systems stacked at effective traps, all which point out the direction of exploration
4. The comprehensive prediction technology for natural gas enrichment belt of super tight reservoir in deep formation, the recognition technology for fractural reservoir and gas prediction geophysical method & technology have been developed and formed.
5. Some key technologies of productivity evaluation, well net optimization, water controlling & discharge and reservoir modification, drilling, completion and reservoir protection have been improved & perfected.
引文
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2．邓康龄等，四川盆地地质结构与天然气藏勘探新领域区划研究“八五”国家重科技攻关项目一级专题成果报告，1995．5。
3．安凤山等，四川盆地西部碎屑岩领域天然气富集规律及大型气田预测与评价，“八五”国家重点科技攻关项目一级专题成果报告，1995．5。
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