莺歌海盆地东方区超压流体泄放及油气成藏效应

发布时间：2018-05-08 10:50

本文选题：压力-应力耦合 + 超压流体泄放　；参考：《中国地质大学》2016年博士论文

【摘要】：莺歌海盆地位于华南板块、巽他板块、南海海盆的三角连接带,具有丰富的油气资源储量。高温高压严重制约着莺歌海盆地的油气勘探成功率,而探寻盆地内超压流体泄放机制、过程及伴生油气成藏效应则可科学、有效地规避勘探风险。本文利用莺歌海盆地东方区丰富的钻、测井资料,通过揭示原位压力、应力状态,探究压力-应力关联性,论证了超压流体泄放机制；结合莺歌海盆地东方区三维地震反射数据体,宏观识别、归纳超压流体泄放构造(结构)特征、分布规律,恢复了超压流体泄放的时空过程;基于东方区不同压力-应力状态油气藏的气体地球化学、岩石或矿物学微观对比,揭示了东方区超压流体泄放过程伴生的油气成藏效应。取得的主要认识如下：1、走滑应力体制下,东方区超压封存能力较强,中新统普遍存在强超压。垂向主应力均大于相应深度的最小主应力量级,但小于或接近相应深度的WNW-ESE向最大水平主应力量级,整体处于走滑应力体制。近E-W向水平挤压受控于巽他地块、华南板块的水平位移,时间上起源于中新世早期。东方区中新统压力梯度普遍高于17 MPa/km,部分构造高点的压力处于接近或略微超过相应深度最小主应力(或最小水平主应力)的临界状态,具备水力裂缝形成的条件。东方区的区域压力-应力耦合系数为0.7,近似于南海西南部地区(约0.66),但显著高于南海南部文莱近海区(0.58)。走滑挤压应力体制下东方区的超压封存能力弱于走滑或逆冲挤压更为显著的南海南部俯冲带,但仍强于具有理想伸展应力体制的地区。2、东方区发育垂向管柱体和气烟囱两类超压流体泄放构造。西缘上斜坡区大量管柱体刺穿上中新统,并终止于上新统底面；中央隆起高部位气烟囱刺穿或终止于上新统。垂向流体泄放构造的发育在时间上与中新统超压的发育、烃源岩的生烃以及构造活跃相耦合。垂向流体泄放构造的时空差异分布,指示晚中新世超压流体大规模向西缘上斜坡运移,而上新世以来大规模向中央隆起高点汇聚。走滑挤压作为外在触发机制对东方区垂向泄放构造的形成必不可少。一方面,挤压强度的垂向差异,可导致深层二次增压强(水平挤压增压),浅层二次增压弱；另一方面,构造挤压导致的砂体超过约500 m的翘倾、抬升加速了深层强超压流体向浅层高点的汇聚,形成的局部压力-应力耦合；二者的联合作用足以扰动浅层弱超压的区域压力-应力耦合作用,形成水力破裂。3、东方区C1、C2气田超压油气保存能力不同,系统开放程度差异,并导致气体组分、碳同位素分异,上中新统砂岩成岩过程、矿物组分差异。①C1气田超压油气保存能力小于6 MPa,甚至达到0,而C2气田超压油气保存能力普遍高于约6MPa～7MPao C1、C2气田超压油气保存能力不同,指示了系统开放程度差异。②C1、C2气田具有相同的烃源岩,但是组分、同位素分析表明：C2气田所有烃气样品的11个参数随成熟度增加均一偏移；而C1气田所有烃气样品的δ¨n-iC4相对于成熟度增加负偏特征显著,其余10个参数随成熟度增加一致正向偏移。C1气田烃气的δ13n-iC4负偏,违背了封闭热解实验中丁烷同分异构体在成熟度增加过程中nC4/iC4增大、813nC4和813iC4偏重、δ13nC4/513iC4增大的趋势,指示了高系统开放程度下烃气散失的发生。高开放程度系统中烃源岩低熟熟阶段生成气体难以保存,而高熟烃气或过熟无机二氧化碳相对富集；低开放程度(封闭)系统内,烃源岩不同成熟阶段生成气体均会被高效保存,但大量低成熟度阶段烃气、氮气的优先富集会较大程度地稀释高熟烃气或过熟无机二氧化碳。③C1、C2气田上中新统砂体均来源于越东物源区,经历相同的搬运、沉积过程,但薄片统计或X衍射分析表明：C1气田上中新统砂岩长石颗粒、绿泥石含量偏低,高岭石、伊蒙混层偏高,富含铁白云石胶结；C2气田上中新统砂岩长石颗粒、绿泥石含量偏高,高岭石、伊蒙混层含量偏低,富含方解石胶结。C1气田上中新统砂岩长石颗粒、绿泥石含量低于C2气田,指示了相对更强烈的溶蚀。绿泥石的溶蚀释放大量Mg2+、Fe2+,有助于富Mg-Fe的碳酸盐岩在C1气田上中新统砂岩内沉淀、胶结。C1气田上中新统砂岩在强烈溶蚀下仍富集对K+非常敏感的伊蒙混层、高岭石,表明溶蚀-沉淀过程中存在K+的流失。盐水包裹体均一温度介于110℃～170℃范围时,C1气田上中新统砂岩内卤水盐度低于C2气田,也表明C1气田上中新统砂岩卤水中溶质流失。高开放程度下卤水泄放直接导致了C1气田上中新统砂岩内成岩过程中的物质流失、溶蚀-沉淀物质不均衡。尽管高开放程度下的卤水泄放改善了C1气田上中新统砂岩孔隙物性,但孔隙度仅提高1vo1%～4 vo1%,且物性改善时期不早于烃类充注期,因此,孔隙改善对油气成藏的实质性贡献有限。
[Abstract]:Yinggehai basin is located in the Southern China plate, the Sunda plate and the triangular connection zone of the South China Sea basin, which has rich reserves of oil and gas. High temperature and high pressure seriously restricts the success rate of oil and gas exploration in Yinggehai basin, and the exploration of overpressure fluid drainage mechanism in the basin, process and associated oil and gas accumulation effect can be scientific and effective to avoid exploration risk. With the rich drilling and logging data in the Orient area of Yinggehai basin, Wen Li demonstrated the pressure and stress correlation in situ, explored the pressure stress correlation, demonstrated the overpressure fluid discharge mechanism, and combined with the 3D seismic reflection data in the Orient area of Yingge basin, the macroscopic recognition, the induction of overpressure fluid discharge structure (structure), distribution law and recovery. The space-time process of overpressure fluid drainage is carried out. Based on the gas geochemistry of the oil and gas reservoirs in different pressure stress states of the eastern region, the microcosmic comparison of rock and mineralogy reveals the associated oil and gas accumulation effect in the process of overpressure fluid discharge in the eastern region. The main understanding is as follows: 1, under the strike slip stress system, the ability of overpressure in the eastern region is stronger, There is a general strong overpressure in the middle Miocene. The vertical main stress is greater than the minimum main stress level of the corresponding depth, but the WNW-ESE to the maximum horizontal main strength level is less or closer to the corresponding depth, and the whole is in the strike slip stress system. The near E-W horizontal extrusion is controlled by the Sunda block, and the horizontal displacement of the Southern China plate is originated in the early Miocene. The pressure gradient of the middle Miocene in the eastern region is generally higher than that of 17 MPa/km, and the pressure of some structural high points is near or slightly above the minimum principal stress (or the minimum horizontal principal stress) at the corresponding depth, and has the condition of the formation of hydraulic fractures. The regional pressure stress coupling coefficient of the eastern region is 0.7, approximately in the southwest of the South China Sea (about 0.66). But it is significantly higher than the southern Brunei coastal area (0.58) in South China Sea. The overpressure sealing ability of the eastern region under the strike slip extrusion stress system is weaker than the southern subduction zone of the South China Sea, which is more significant than the strike slip or thrust extrusion. But it is still stronger than the.2 in the area with ideal extensional stress system, and two types of overpressure fluid discharge structures are developed in the vertical tube and gas chimney in the East. A large number of tubular columns in the upper slope of the west edge pierce the middle Miocene and terminate at the bottom of the upper Miocene; the high position gas chimneys of the central uplift pierce or terminate in the upper Miocene. The development of the vertical fluid discharge structure is coupled with the development of overpressure in the middle and the Miocene, the hydrocarbon generation of the source rocks and the active phase of the structure. Distribution, indicating that the late Miocene superpressure fluid was migrated to the upper slope of the western margin in a large scale, while the upper part of the upper part of the Pliocene converged to the high point of the central uplift. As an external triggering mechanism, the strike slip extrusion is essential for the formation of vertical discharge structures in the East. On the one hand, the vertical difference of the compressive strength can lead to two intensities in the deep level. On the other hand, the sand body of the shallow layer is weak two times; on the other hand, the sand body caused by the tectonic extrusion is more than 500 m, and the uplift accelerates the convergence of the deep deep overpressure fluid to the shallow height, and the local pressure stress coupling is formed. The joint action of the two is sufficient to disturbance the pressure stress coupling effect of the shallow weak overpressure in the region, and the hydraulic fracture.3 is formed in the East. The storage capacity of overpressure oil and gas in C1, C2 gas field is different, and the opening degree of the system is different, and the gas composition, carbon isotope differentiation, the upper middle Neocene sandstone formation process and the mineral composition difference. (1) the storage capacity of overpressure oil and gas in C1 gas field is less than 6 MPa, even up to 0, while the storage capacity of super pressure oil and gas in C2 gas field is generally higher than that of about 6MPa to 7MPao C1, C2 gas field The preservation ability of overpressure oil and gas is different, indicating the difference of opening degree of the system. (2) C1, C2 gas field has the same hydrocarbon source rocks, but the composition and isotopic analysis show that the 11 parameters of all hydrocarbon gas samples in C2 gas field increase uniformly with maturity, and the Delta n-iC4 of all hydrocarbon gas samples in C1 gas field is marked by the negative bias of increase relative to maturity. The other 10 parameters increase the negative deviation of the hydrocarbon gas of.C1 gas field with the uniform forward migration with the maturity. It is contrary to the increase of nC4/iC4, the weight of 813nC4 and 813iC4 and the increase of delta 13nC4/513iC4 in the process of increasing the maturity of the butane isomers in the closed pyrolysis experiment, indicating the occurrence of hydrocarbon gas loss under the open degree of the high system. In the low maturity stage of the hydrocarbon source rock, the formation gas is difficult to be preserved, while the high mature hydrocarbon gas or the over ripe inorganic carbon dioxide is relatively enriched. In the low open degree (closed) system, the gas generated from the different mature stages of the source rock will be efficiently preserved, but the preferential enrichment of nitrogen gas in a large number of low maturity stages will dilute the high maturity to a large extent. Hydrocarbon gas or over ripe inorganic carbon dioxide. (3) C1, the middle Miocene sand body in C1, C2 gas field all originate from Yu Yue East material source area, experience the same transport and deposition process, but the thin slice statistics or X diffraction analysis shows that the content of the Miocene sandstone feldspar particles in the C1 gas field is low, kaolinite, imimon mixed layer is high, rich in ferric dolomite cementation, C2 gas field The content of the Miocene sandstone feldspar, the chlorite content is high, the kaolinite and the imimon mixed layer is low, which is rich in the middle Miocene sandstone feldspar particles in the calcite cementing.C1 gas field. The chlorite content is lower than the C2 gas field, indicating a relatively stronger dissolution. The dissolution of the chlorite releases a large amount of Mg2 + and Fe2+, which helps the rich Mg-Fe carbonate rocks in the C1 gas field. The Miocene sandstone in the cemented.C1 gas field is still enriched in the cemented.C1 gas field and is still enriched with K+ sensitive imimon. Kaolinite indicates that there is a loss of K+ in the process of dissolution and precipitation. The salinity of the middle Miocene sandstone in the C1 gas field is lower than that of C2 gas field, and also indicates C1 gas in the upper Miocene sandstone in the C1 gas field. The high open degree of brine discharge directly leads to the loss of material in the sandstone internal formation of the upper Miocene sandstone in C1 gas field, and the dissolution and precipitation material is unevenly. The porosity of the Miocene sandstone in the C1 gas field is improved by the high open degree of brine relief, but the porosity is only 1vo1% to 4 vo1% And the improvement period of physical property is not earlier than hydrocarbon filling period. Therefore, the pore improvement has limited contribution to hydrocarbon accumulation.

【学位授予单位】：中国地质大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：P618.13

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