【作者】 刘士忠；

【导师】 查明；

【作者基本信息】 中国石油大学 ， 地质资源与地质工程， 2008， 博士

【摘要】 济阳坳陷深层一般指3500m以下的层位,主要以勘探下第三系的裂解气为主。近几年,济阳坳陷深层天然气勘探不断有新的发现,特别是2007年新利深1井的勘探成功,说明深层天然气勘探具有较大的潜力。保存条件为天然气成藏的主要控制因素之一,因此系统研究保存条件的定量评价方法对深层天然气的勘探具有重要意义。本文以大量的实际地质资料和实验数据为基础,通过应用石油地质学、数学、渗流力学及测井解释等多学科理论,主要探讨了研究区的盖层封盖性、断层封闭性及地层水条件。建立了盖、储层的阻力、气藏驱动力的地质模型及计算模型,提出了利用盖、储层之间阻力与驱动力差值来综合评价盖层封闭性的方法,对研究区深层天然气的盖层封闭能力进行了综合评价。泥岩盖层封闭油气的作用不仅仅表现在现在,更重要是在主要成藏期和油气藏形成之后所起的作用如何,对于研究油气藏的形成与保存才更有意义。依据泥岩声波时差与埋深的关系,研究了超压泥岩盖层目前封闭能力及其封闭能力的演化,客观地评价了超压泥岩盖层对油气封闭的有效性;断层的封闭性则利用断面压力、砂泥对接概率方法及断裂带泥质含量方法来进行研究,评价了济阳坳陷主要控油断层断层的封闭性能,得到了令人满意的结果。源岩、盖层和断裂是断陷盆地中油气保存成藏的主控因素,其条件优劣及它们彼此在时间和空间上的匹配关系如何,在一定程度上制约着断陷盆地油气运聚成藏的数量及空间分布。在盖层封盖性、断层封闭性及其演化研究的基础上,开展了济阳坳陷深层源、盖、断时空匹配关系对油气运聚成藏控制作用研究。主要包括以下几个方面:(1)通过对济阳坳陷沙一段、沙三中下亚段及沙四上亚段泥岩盖层宏观封闭性、微观封闭性及盖层封闭性综合评价研究,表明这三套盖层有利保存区主要分布在各洼陷的深部。东营凹陷盖层封闭能力由南向北逐渐变好,有利区主要分布在利津洼陷、民丰洼陷,其次为牛庄洼陷,而沾化凹陷有利保存区主要分布在渤南洼陷及五号桩洼陷。(2)从气体逸散的力学机制出发,将天然气通过盖层的逸散划分为驱替及渗滤两个阶段,前者为天然气排驱地层水的驱替阶段,后者为气体的渗滤阶段。当气藏驱动力不能突破盖层封闭阻力时,气藏表现为静态封闭状态;当气藏驱动力突破盖层封闭阻力时,则气藏表现为动态封闭状态。动态封闭状态中天然气散失量主要取决于渗滤阶段的逸散量,由此确定了盖层厚度、驱替时间、渗滤时间等影响因素在天然气逸散中的重要性,并由此建立了定量评价模型,评价了济阳坳陷下第三系泥岩盖层的封闭性。(3)在超压形成与演化分析的基础上,对超压泥岩盖层封闭性演化规律进行了定量研究。超压泥岩盖层封闭性演化是按阶段进行的,每一次超压释放表明上一次封闭性演化阶段的结束,下一次封闭性演化阶段的开始。每一次演化过程中封闭性逐渐增强,在超压释放期封闭性降至最低点。研究超压泥岩盖层封闭性演化规律不仅可以准确评价目前封闭能力和预测封闭能力演化,而且还可以研究封闭油气的有效性。利用声波时差资料,计算了东营凹陷下第三系泥岩超压的释放次数及深度,客观地评价了沙三段泥岩盖层的封闭能力及其对油气成藏的控制作用。结果表明:①东营凹陷沙三段泥岩超压形成于沙一期-东营早期,而深部源岩的大量排烃期为馆陶期,超压形成期比排烃期早,因此超压泥岩能够有效地封闭烃源岩大量生成的油气。②沙三段泥岩超压在馆陶末期发生第一次释放,之后,泥岩愈合,超压再次增加,目前正处于第二次超压演化过程中。③现今沙三段泥岩超压值约为8MPa,具有较强的超压封闭能力,是深层油气成藏的重要条件之一。(4)以断层的封闭机制为线索,用断面应力分析、泥岩涂抹等方法,研究了济阳坳陷主要控油气断层断层的封闭性,以断层生长速率法研究了济阳坳陷断层的主要活动期。研究表明济阳坳陷断层现今主要表现为封闭性,断层的主要活动期出现在沙三段及沙一段沉积时期,从断层活动消亡时期看,多数断层均于馆陶组沉积时衰减、消亡。济阳坳陷源、盖、断时空匹配关系研究表明,断层活动期早于生气高峰期及盖层封闭形成期,盖层封闭形成期早于生气高峰期,对深部天然气的保存有利。(5)随沉积盆地的形成与演化,水动力场也有形成、发展和消亡的过程。东营凹陷深层水动力条件及古水文地质参数的研究表明,东营凹陷地下水动力场在平面上呈对称性:总体上大气水由凹陷边缘向凹陷中心渗入,凹陷内部各洼陷为压榨水形成的离心流区,凹陷边缘南部斜坡带和北部断阶带以及凹陷内部中央断裂带为越流泄水区。纵向上,局部水动力单元强度及演化规律与地层的埋藏深度有关,随着埋藏深度的增加,水动力单元强度逐渐减弱。洼陷的深层具稳定的水动力条件,以氯化钙(Cacl2)型水占比例大,环境相对闭塞,流体交替能力小,封存能力强,有利于深层天然气的保存。在盖层、断层和水动力条件对油气分布控制作用研究的基础上,结合生烃、储层等方面的资料,对济阳坳陷深层天然气的有利保存区进行了评价,得到东营凹陷北部陡坡带西段及东段,沾化凹陷的渤南洼陷为深层天然气的有利保存区域。生气中心及周缘广泛分布的岩性圈闭以及围绕生气中心在沙三段下亚段以下层位发育的古构造、构造—岩性圈闭是天然气勘探的主要方向。更多还原

【Abstract】 The deep layer is currently distributed at burial depth of >3500 meter in Yiyang basin, and the main explorative object is finding cracking gas in lower Tertiary. New researches have obtained many important results, especially in the well of Xinlishen 1, so the natural gas exploration of deep layer has great potential in Jiyang basin. A good preservation of trapped hydrocarbons is a main controlling on oil/gas accumulation. Quantitative study on preservation ability is very significant for the natural gas exploration of deep layer.Based on a large amount of data obtained from geology and experiment, a study of caprock sealing, fault sealing and hydrodynamic conditions has been made, with the application of theories from multi-disciplines, such as geology, mathematics and mechanics. The mathematical models for resistance of caprock and gas potentical energy of reservoir have been built. An evaluation method of the sealing ability of caprocks is put forward by the difference between the resistance of caprock and gas potentical energy of reservoir. The sealing ability of caprocks is very significant for the preservation and destruction of trapped hydrocarbons not only for the present, but also for the time after the oil/gas accumulated. With the use of acoustic logging data, this paper analyzed the sealing ability of poorly-compacted mudstone and its evolvement, and effectiveness of sealing ability has been explained. Fault sealing ability is studied through normal stress of fault surface, lithology face-to-face of two plates, and muddy contents in faulted belt.The analysis results show that the fault sealing ability is main factor impacting oil/gas accumulation in Jiyang basin. Source rocks, caprocks and faults are the main factors of controlling the oil/gas reservoir forming in faulted basin. The time-space matching relation of the source rocks, caprocks and faults control the oil/gas accumulation size and the distribution scope. By analyzing the time-space matching relation of the source rocks, caprocks and faults, their effect on oil/gas reservoir forming and distribution was studied in Jiyang basin. The following important progresses have been extended.(1)The mudstone caprocks of the deep part in Shahejie formation developed well and have better sealing abilities. The sealing ability and the lateral continuity of caprocks of Es1, Es3 and Es4 members are good so they can serve as caprocks for the underlying gas reservoir. The regions of having medium or good sealing ability of caprocks are Lijin-Minfeng subsag, Niuzhuang subsag, Bonan and Wuhaozhuang subsag.(2) Based on the mechanism of the percolation mechanics , the gas leakage through caprock can be divided into two stages: the displacement and the percolation. When the residual pressure in the gas reservoir is less than the critical displacement pressure in the caprock, the gas reservoir is covered in a static state; conversely, it is in a dynamic state. The loss amount of natural gas in the dynamic state lies on the leakage loss amount of natural gas, so the caprock thickness, the displacement time and the percolation time play very important roles in gas leakage. This paper, therefore, developed a quantitative evaluation model for the gas leakage, and estimated the sealing ability of caprocks of lower Tertiary in Jiyang basin.(3) Based on the analysis of formation and evolution of overpressure,the evolution law for sealing of overpressured mudstone caprock was quantitatively studied. The result showed that sealing of overpressured mudstone caprock evolved in stages.Each release of overpressure indicated the end of an old evolution stage and the beginning of a new evolution stage.Sealing of overpressured mudstone caprock increased gradually in each evolution process, and it was the worst at the release period of overpressure.The study of evolution for sealing of overpressured mudstone caprock can not only determine exactly sealing ability and forecast sealing evolution,but also study sealing efficiency for oil/gas accumulation. With the use of acoustic logging data,, this paper computed the release times and the release depth of overpressure of Es3 member in Dongying depression,and estimated the sealing ability of overpressured mudstone caprock of Es3 member and its’controlling on oil/gas accumulation. The results are as following:①the beginning period of pressure sealing formation of Es3 member is earlier than the period of the main hydrocarbon expulsion of source rocks of deep layer, and the sealing ability of mudstone caprock of Es3 member for oil/gas accumulation is of efficiency;②the overpressured mudstone in Es3 member released one times,and it is in the second evolution stage now. The sealing of overpressured mudstone caprock increases with increasing overpressure;③the sealing ability of caprock of Es3 member is good , with 8.0 MPa overpressure, and it is one of the main controlling factors on oil/gas accumulation in deep layer.(4) Based on the fault sealing mechanism, this paper studied the sealing ability of main faults in Jiyang basin through normal stress of fault surface, lithology face-to-face of two plates, and muddy contents in faulted belt. The fault intensity was studied depended on the growth index and fault activity rate. The results indicate that the faults in Jiyang basin have strong sealing abilities. The fault intensity was strong during the sedimentating of Es3 and Es1 members,and died out during the sedimentating of Guantao formation. The time-space matching relation of the source rocks, caprocks and faults is good, and it is favorable for oil/gas from deep layer to accumulate and preservate.(5) Accompanying the origin and evolution of sedimentary basin, hydrodynamic field underwent a process of origin, development and perished. By studying the hydrodynamic conditions and the palaeohydrogeogical parameters, the hydrodynamic field in the Dongying depression was symmetrical,with the characteristics of gravity-induced centripetal flow recharged by meteoric water along the edges of the depression, centrifugal flow formed by compaction in the central depression area, and cross-formational flow and concentration by evaporation in the southern slope and northern fault ramp along the basin margins and the central fractural zone in the interior depression area. The intensity of hydrodynamics had the property of vertical zoning. The intensity weakened gradually with the increasing depth. The deep layer of Dongying depression has steady hydrodynamic conditions, with the CaCl2 water type, and it is favorable for natural gas accumulation.Based on the researches on the sealing ability of caprock, the sealing ability of fault ,the hydrodynamic conditions and the data of source rocks and reservoirs, this paper estimated the favorable areas for natural gas accumulation in Jiyang basin. The west and east portions in North Steep Slope of Dongying depression and the Bonan subsag are favorable for natural gas accumulation and preservation. Main exploration orientations are the lithology traps distributed widely in the gas-generating center and the margin,palaeostructural and structural-lithological traps developed below the lower Es3 member around the gas-generating center.更多还原