【作者】 王艳忠；

【导师】 陈世悦； 操应长；

【作者基本信息】 中国石油大学 ， 地质学， 2010， 博士

【摘要】 次生孔隙发育带的成因及演化是中深层优质储层评价和油气勘探部署的重要依据。一个含油气盆地往往发育多个次生孔隙发育带,目前普遍认为埋藏相对较浅、与有机质演化成熟阶段相对应的第一个次生孔隙发育带为有机酸溶解长石和碳酸盐胶结物成因;而对深层次生孔隙发育带的成因存在不同的观点,一种观点认为深层次生孔隙发育带为深层溶蚀成因,另一种观点认为深层次生孔隙发育带为浅层形成、保存至深层的古次生孔隙发育带。如果对次生孔隙发育带成因及演化认识不清,将直接影响中深层油气勘探成功率。因此,开展次生孔隙发育带成因机制及演化模式研究对中深层油气勘探具有重要的理论指导意义。本论文以东营凹陷北带古近系沙三中亚段～沙四段砂砾岩体为研究对象,综合运用岩心观察、薄片鉴定、图像分析、扫描电镜观察、流体包裹体分析、粘土矿物分析、镜质体反射率测试和岩心物性分析等多种技术方法,结合构造演化史、有机质热演化史、油气成藏史等研究成果,对中深层次生孔隙发育带的形成机制和演化模式进行了系统研究。次生孔隙发育带指次生孔隙百分含量大于50%的高孔隙度储层(或称为有效储层)集中发育带。据此,研究发现民丰洼陷北带沙四段次生孔隙发育带最为典型,共发育四个次生孔隙发育带,其中,沙四上亚段发育次生孔隙发育带Ⅰ、Ⅱ,深度范围分别为2800m-3500m、3750m-4050m;沙四下亚段发育次生孔隙发育带Ⅲ、Ⅳ,深度范围分别为4300m-4500m,4700m-4900m。因此,论文以民丰洼陷北带沙四段次生孔隙发育带为重点展开论述。民丰洼陷北带沙四段次生孔隙发育带储层均为近岸水下扇扇中辫状水道砂砾岩,次生孔隙主要为长石溶解孔隙,其次为碳酸盐胶结物溶解孔隙,发育少量石英溶解孔隙、黄铁矿溶解孔隙和裂缝。次生孔隙发育带Ⅰ、Ⅱ内储层主要为油层,少量为油水同层和含油水层;次生孔隙发育带Ⅲ、Ⅳ内储层均为气层。次生孔隙发育带Ⅰ、Ⅱ储层成岩作用以长石溶解强烈、碳酸盐胶结物充填长石溶解孔隙现象普遍、碳酸盐胶结物溶解为典型特征;次生孔隙发育带Ⅲ、Ⅳ内储层成岩作用以大量沥青和黄铁矿充填孔隙、碳酸盐自形程度高、溶解作用弱、长石溶解弱及其溶解孔被碳酸盐充填现象不明显为典型特征。次生孔隙发育带Ⅰ、Ⅱ内储层经历了“碱性-酸性-碱性-酸性-弱碱性”、“常压-常压-常压”、“地温升高-降低-升高”的成岩环境演化,具有“压实作用/黄铁矿胶结/菱铁矿胶结/石膏胶结→长石溶解/石英次生加大→碳酸盐胶结/石英溶解/长石加大→碳酸盐和长石的溶解/黄铁矿胶结”的成岩作用演化序列特征。次生孔隙发育带Ⅲ、Ⅳ内储层经历了“碱性-酸性-碱性-酸性-弱酸性”、“常压-超压-常压”、“升温-降温-升温”的成岩环境演化,具有“压实作用/硬石膏胶结/石盐胶结/黄铁矿胶结/菱铁矿胶结→长石溶解/石英加大→碳酸盐胶结/石英溶解/长石加大→碳酸盐溶解/长石溶解/石英加大→黄铁矿胶结和沥青充填”的成岩作用演化序列特征。在次生孔隙发育带成岩环境演化和成岩作用序列研究的基础上,分别建立了沙四上亚段和沙四下亚段成岩环境演化及储层改造模式。次生孔隙发育带Ⅰ、Ⅱ为近岸水下扇沉积旋回中上部扇中辫状水道砂体中部储层在早期有机酸作用下形成大量次生孔隙,演化成以原生孔隙为主的孔隙发育带,之后受到碳酸盐胶结轻微破坏形成古次生孔隙发育带,在地层抬升过程中古次生孔隙发育带又经历了有机酸的再次溶解改造,最后油气充注成藏对次生孔隙发育带进行保护,形成现今次生孔隙发育带,其成因机制可概括为“酸溶为主、碱溶为辅、早期成孔、早期成带”,演化概括为“早期成因-多期改造-晚期油气充注保护”型演化模式。次生孔隙发育带Ⅲ、Ⅳ为近岸水下扇沉积旋回中上部扇中辫状水道砂体中部储层在早期有机酸作用下形成以原生孔隙为主(次生孔隙绝对量较大)的孔隙发育带,由于油气早期充注和超压的保护,在地层抬升和再次沉降过程中受轻微改造,直到深埋藏(埋深大于4000m,地层温度大于160℃)时“古油藏”原油裂解形成大量沥青和黄铁矿充填原生孔隙后才形成的现今次生孔隙发育带,其成因机制可概括为“酸溶为主、碱溶为辅、早期成孔、晚期成带”,其演化可概括为“早期油气充注-超压保护-晚期成因”型演化模式。更多还原

【Abstract】 The genesis and evolution of secondary pore development zone is important basis for the high-quality reservoir evaluation and the deployment of oil and gas exploration in mid-deep formation. Generally, several secondary pore development zones are developed in a petroliferous basin. At present, it is considered that feldspar and carbonate cements dissolved by organic acids is the cause of the first secondary pore development zone corresponding to organic matter maturity in shallow formation. While,there are two views on the causes of deep secondary pore development zones. One is that deep secondary pore development zones were formed in deep formation;Another is that deep secondary pore development zones were the secondary pore development zones forming in the shallow formation and preserved to the deep formation. If the genesis and evolution of secondary pore development zones can’t be determined, the success rate of hydrocarbon exploration will be affected a lot. So the research on the genetic mechanism and evolution model of secondary pore development zones has great leading significance in theory for oil and gas exploration in mid-deep formation. This dissertation focused on the case study of the sand-conglomerate body of the middle part of Es3z～Es4 of Paleogene in Dongying depression. Based on a conjunction of core observation, thin section identification, image analysis, SEM observation, fluid-inclusion analysis, core X-ray analysis, testing of vitrinite reflectance and core properties analysis and other methods, and the research achievements as the tectonic evolution history, thermal evolution of organic matters, and the history of hydrocarbon accumulation, the genetic mechanism and evolution model of secondary pore development zones in mid-deep formation were systematically studied.Secondary pore development zone is defined as the zone where high porosity reservoirs (also called effective reservoirs), whose secondary pore is more than 50%, intensively develops. Accordingly, the study shows that the secondary pore development zone in Es4 of Minfeng sag is most typical. It develops 4 secondary pore development zones totally. The secondary pore development zoneⅠandⅡdevelops in Es4s, the depth range of which is 2800m-3500m and 3750m-4050m. The secondary pore zoneⅢandⅣdevelops in Es4x, the depth range of which is 4300m-4500m and 4700m-4900m. So this dissertation focus on the discussion of the secondary pore development zones of Es4 in Minfeng sag.The reservoirs of the secondary pore development zones in Es4 in Minfeng sag are sand - conglomerate of braided channel in nearshore subaqueous fan, and the secondary pores of which are mainly feldspar dissolution pores, secondly carbonate cement dissolution pores, a few quartz dissolution pores, pyrite dissolution pores and cracks. The reservoirs of secondary pore zoneⅠandⅡare mainly oil reservoirs, and secondly a few oil-water layers and oil-bearing water layers. The reservoirs of secondary pore zoneⅢandⅣare gas layers. The typical diagenetic characteristics of reservoirs in secondary pore development zoneⅠ,Ⅱis that the feldspar dissolution is strong, the phenomenon that feldspar dissolution pores filled by carbonate cements is common, and carbonate cements dissolution is obvious. The typical diagenetic characteristics of reservoirs in secondary pore development zoneⅢandⅣis that a lot of pores were filled by asphalt and pyrite, carbonate cements are high-shaped and dissolved weakly, feldspars are also dissolved weakly, and the phenomenon that feldspar dissolution pores filled by carbonate cements is not obvious. The reservoirs in secondary pore development zoneⅠandⅡexperienced the diagenetic environment with“alkaline-acid-alkaline-acid-weak alkaline”,“normal pressure - normal pressure - normal pressure”,“formation temperature increasing - decreasing - increasing”, and diagenetic evolution sequence of which is“compaction / pyrite cementation / siderite cementation / gypsum cementation→feldspar dissolution / quartz overgrowth→carbonate cementation/ quartz solution / feldspar overgrowth→carbonate and feldspar late period solution / pyrite cementation”. The reservoirs in secondary pore development zoneⅢandⅣexperienced the diagenetic environment with“alkaline - acid -alkaline-acid-weak acid”,“normal pressure - overpressure-normal pressure”,“formation temperature increasing-decreasing-increasing”, and diagenetic evolution sequence of which is“compaction / gypsum cementation / halite cementation / gypsum cementation / pyrite cementation / siderite cementation→feldspar dissolution / quartz overgrowth→carbonate cementation / quartz solution / feldspar overgrowth→carbonate dissolution / feldspar dissolution / quartz overgrowth→pyrite cementation and asphalt filling”.Based on the research of the diagenetic environment evolution and the diagenetic sequence of the secondary pore development zones, the models of diagenetic environment evolution and reservoir reconstruction in Es4s and Es4x have been established respectively. The genetic mechanism of the secondary pore development zoneⅠandⅡis that the middle reservoirs of brained channels of mid-fan of nearshore subaqueous fan in middle-upper part of sedimentary cycle formed pore development zone with the primary pore in leading position because of massive secondary pore formed by early organic acid dissolution, and because of the slight destruction of primary pore by carbonate cementation, the pore development zone formed the paleo secondary pore development zone, which experiences the dissolution effect again by organic acid in the process of strata uplifting, and the paleo secondary pore development zone formed the present secondary pore development zone finally due to the protection of hydrocarbon charging. The genetic mechanism of the secondary pore development zoneⅠandⅡcan be summarized as“dissolution in acidic environments is main, dissolution in alkaline environment is secondary, secondary porosity formed in early stage, secondary porosity development zone formed in early stage”.The evolution model he secondary pore development zoneⅠandⅡcan be summarized as“early generated-multiple phase deformation-late hydrocarbon charging protection”. The genetic mechanism of the secondary pore development zoneⅢandⅣis that the middle reservoirs of brained channels of mid-fan of nearshore subaqueous fan in middle-upper part of sedimentary cycle formed the pore development zone with the primary pore in leading position (the absolute amount of secondary pore is high) because of the early organic acid effect, and because of early hydrocarbon charging and overpressure protection, the pore development zone was slightly transformed during the process of strata uplifting and resettlement, and the pore development zone finally formed the present secondary pore development zone due to the filling of primary pore by massive asphalt and pyrite from oil cracking of deep buried paleo-reservoirs (the buried depth was more than 4000m and the formation temperature was more than 160℃). The genetic mechanism of the secondary pore development zoneⅢandⅣcan be summarized as“dissolution in acidic environments is main, dissolution in alkaline environment is secondary, secondary porosity formed in early stage, secondary porosity development zone formed in early stage”.The evolution model of the secondary pore development zoneⅢandⅣcan be summarized as“early hydrocarbon charging- overpressure protection-late cause”.更多还原