Influences of burial process on diagenesis and high-quality reservoir development of deep-ultra-deep clastic rocks:A case study of Lower Cretaceous Qingshuihe Formation in southern margin of Junggar Basin,NW China

Taking the Lower Cretaceous Qingshuihe Formation in the southern margin of Junggar Basin as an example,the influences of the burial process in a foreland basin on the diagenesis and the development of high-quality reservoirs of deep and ultra-deep clastic rocks were investigated using thin section,scanning electron microscope,electron probe,stable isotopic composition and fluid inclusion data.The Qingshuihe Formation went through four burial stages of slow shallow burial,tectonic uplift,progressive deep burial and rapid deep burial successively.The stages of slow shallow burial and tectonic uplift not only can alleviate the mechanical compaction of grains,but also can maintain an open diagenetic system in the reservoirs for a long time,which promotes the dissolution of soluble components by meteoric freshwater and inhibits the precipitation of dissolution products in the reservoirs.The late rapid deep burial process contributed to the development of fluid overpressure,which effectively inhibits the destruction of primary pores by compaction and cementation.The fluid overpressure promotes the development of microfractures in the reservoir,which enhances the dissolution effect of organic acids.Based on the quantitative reconstruction of porosity evolution history,it is found that the long-term slow shallow burial and tectonic uplift processes make the greatest contribution to the development of deep-ultra-deep high-quality clastic rock reservoirs,followed by the late rapid deep burial process,and the progressive deep burial process has little contribution.

Action mechanisms of abnormal fluid pressure on physical properties of deep reservoirs: A case study on Jurassic Toutunhe Formation in the southern margin of Junggar Basin, NW China

Considering the action mechanisms of overpressure on physical changes in skeleton particles of deep reservoir rocks and the differences in physical changes of skeleton particles under overpressure and hydrostatic pressure, the sandstone of the Jurassic Toutunhe Formation in the southern margin of Junggar Basin was taken as an example for physical modeling experiment to analyze the action mechanisms of overpressure on the physical properties of deep reservoirs. (1) In the simulated ultra-deep layer with a burial depth of 6000-8000 m, the mechanical compaction under overpressure reduces the remaining primary pores by about a half that under hydrostatic pressure. Overpressure can effectively suppress the mechanical compaction to allow the preservation of intergranular primary pores. (2) The linear contact length ratio under overpressure is always smaller than the linear contact length ratio under hydrostatic pressure at the same depth. In deep reservoirs, the difference between the mechanical compaction degree under overpressure and hydrostatic pressure shows a decreasing trend, the effect of abnormally high pressure to resist the increase of effective stress is weakened, and the degree of mechanical compaction is gradually close to that under hydrostatic pressure. (3) The microfractures in skeleton particles of deep reservoirs under overpressure are thin and long, while the microfractures in skeleton particles of deep reservoirs under hydrostatic pressure are short and wide. This difference is attributed to the probable presence of tension fractures in the rocks containing abnormally high pressure fluid. (4) The microfractures in skeleton particles under overpressure were mainly formed later than that under hydrostatic pressure, and the development degree and length of microfractures both extend deeper. (5) The development stages of microfractures under overpressure are mainly controlled by the development stages of abnormally high pressure and the magnitude of effective stress acting on the skeleton particles. Moreover, the development stages of microfractures in skeleton particles are more than those under hydrostatic pressure in deep reservoir. The multi-stage abnormally high pressure plays an important role in improving the physical properties of deep reservoirs.

Coalbed Methane Enrichment Regularity and Major Control Factors in the Xishanyao Formation in the Western Part of the Southern Junggar Basin

There are abundant coal and coalbed methane(CBM)resources in the Xishanyao Formation in the western region of the southern Junggar Basin,and the prospects for CBM exploration and development are promising.To promote the exploration and development of the CBM resources of the Xishanyao Formation in this area,we studied previous coalfield survey data and CBM geological exploration data.Then,we analyzed the relationships between the gas content and methane concentration vs.coal seam thickness,burial depth,coal reservoir physical characteristics,hydrogeological conditions,and roof and floor lithology.In addition,we briefly discuss the main factors influencing CBM accumulation.First,we found that the coal strata of the Xishanyao Formation in the study area are relatively simple in structure,and the coal seam has a large thickness and burial depth,as well as moderately good roof and floor conditions.The hydrogeological conditions and coal reservoir physical characteristics are also conducive to the enrichment and a high yield of CBM.We believe that the preservation of CBM resources in the study area is mainly controlled by the structure,burial depth,and hydrogeological conditions.Furthermore,on the basis of the above results,the coal seam of the Xishanyao Formation in the synclinal shaft and buried at depths of 700-1000 m should be the first considered for development.

Simulation for the Controlling Factors of Structural Deformation in the Southern Margin of the Junggar Basin

According to the differences of structural deformation characteristics, the southern margin of the Junggar basin can be divided into two segments from east to west. Arcnate thrust-and-fold belts that protrude to the north are developed in the eastern segment. There are three rows of en echelon thrust-and-fold belts in the western segment. Thrust and fold structures of basement-involved styles are developed in the first row, and decollement fold structures are formed from the second row to the third row. In order to study the factors controlling the deformation of structures, sand-box experiments have been devised to simulate the evolution of plane and profile deformation. The planar simulation results indicate that the orthogonal compression coming from Bogeda Mountain and the oblique compression with an angle of 75° between the stress and the boundary originating from North Tianshan were responsible for the deformation differences between the eastern part and the western part. The Miquan-Uriimqi fault in the basement is the pre-existing condition for generating fragments from east to west. The profile simulation results show that the main factors controlling the deformation in the eastern part are related to the decollement of Jurassic coal beds alone, while those controlling the deformation in the western segment are related to both the Jurassic coal beds and the Eogene clay beds. The total amount of shortening from the Yaomoshan anticline to the Gumudi anticline in the eastern part is -19.57 km as estimated from the simulation results, and the shortening rate is about 36.46%; that from the Qingshuihe anticline to the Anjihai anticline in the western part is -22.01 km as estimated by the simulation results, with a shortening rate of about 32.48%. These estimated values obtained from the model results are very close to the values calculated by means of the balanced cross section.

Lithofacies paleogeography restoration and its significance of Jurassic to Lower Cretaceous in southern margin of Junggar Basin,NW China

In view of the difficulties in the study of lithofacies paleogeography and the low reliability of the distribution range of sedimentary sand bodies in the prototype basin caused by less deep drilling, complex seismic imaging and low degree of exploration in the southern margin of Junggar Basin, NW China. A new method based on the source to sink idea was used to restore lithofacies paleogeography and predict glutenite distribution. In the restoration, apatite fission track age was used to define range and uplift time of macro-provenance;the range of provenance area and the migration process of lake shoreline were restored based on the quantitative relationship between gravel diameter and transportation distance, tectonic shortening and other geological parameters;drilling cores and field outcrop sedimentary structures were analyzed, and a series of maps of lithofacies paleogeographic evolution and distribution range of glutenite bodies were compiled. It is concluded that from Early Jurassic to Early Cretaceous, in the southern margin of Junggar Basin, the provenance area gradually expanded from south to north, the lake basin expanded, shrunk and expanded, and the paleoclimate changed from humid to drought to humid. The western section always had proximal fan delta deposits from the southern ancient Tianshan provenance developed, and in the middle and eastern sections, the provenance areas evolved from far source to near source, mainly river-delta, braided delta, fan delta and other sediments developed. The boundary between provenance areas of the western and middle sections is speculated to be Hongche fault zone. In an angle open to the northwest with the current basin edge line, the restored ancient lake shoreline controlled the heterogeneity of reservoirs in the delta plain belt and delta front belt on its both sides. The ancient lake shoreline, current stratigraphic denudation line and current basin margin line limit the types and scope of favorable reservoirs.This understanding provides an important geological basis for oil and gas exploration in the deep lower source-reservoir assemblage at the southern margin of Junggar Basin.

Major breakthrough of Well Gaotan 1 and exploration prospects of lower assemblage in southern margin of Junggar Basin, NW China

Well Gaotan 1 was tested a high yield oil and gas flow of more than 1 000 m^3 a day in the Cretaceous Qingshuihe Formation,marking a major breakthrough in the lower assemblage of the southern margin of Junggar Basin. The lower assemblage in the southern margin of the Junggar Basin has favorable geological conditions for forming large Petroleum fields, including:(1) Multiple sets of source rocks, of which the Jurassic and Permian are the main source rocks, with a large source kitchen.(2) Multiple sets of effective reservoirs,namely Cretaceous Qingshuihe Formation, Jurassic Toutunhe Formation and the Khalza Formation etc.(3) Regional thick mudstone caprock of Cretaceous Tugulu Group, generally with abnormally high pressure and good sealing ability.(4) Giant structural traps and litho-stratigraphic traps are developed. The northern slope also has the conditions for large-scale litho-stratigraphic traps.(5) Static elements such as source rocks, reservoirs and caprocks are well matched, and the dynamic evolution is suitable for large oil and gas accumulation. The lower assemblage of the southern margin of the Junggar Basin has three favorable exploration directions, the Sikeshu Sag in the west part, the large structures in the middle and eastern part, and the northern slope.

Formation conditions and exploration direction of large and medium gas reservoirs in the Junggar Basin, NW China

The Junggar Basin is rich in oil but lacks natural gas, which is inconsistent with its geological background of natural gas. Based on the analysis of main source kitchens, and the evaluation of geological setting and controlling factors of gas accumulation, it is proposed that three significant fields for gas exploration should be emphasized. The first field is the Carboniferous volcanic rocks. The Carboniferous residual sags and large-scale reservoirs were developed in three active continental margins, i.e., the southeastern, northeastern and northwestern active continental margins. Gas accumulation is controlled by the favorable reservoir-caprock combinations composed of volcanic rocks and their superimposed lacustrine mudstones in the Upper Wuerhe Formation. Dinan, Eastern and Zhongguai uplifts are three favorable directions for natural gas exploration. The second field is the Lower combinations in the southern margin of Junggar Basin. Rows of structural traps were developed in this area with ideal preservation conditions and space-time configuration for trap-source combinations. Sets of clastic reservoirs and overpressured mudstones formed perfect reservoir-caprock combinations which are the main exploration direction for Jurassic coal-type gas reservoirs in this area. The seven large structural traps in the middle-east section are recently the most significant targets. The last field is the Central Depression. Large hydrocarbon generating centers, i.e., Mahu, Fukang and Shawan sags, were developed in this area, their source rocks were deeply buried and at highly-mature stage. Thus the Central Depression is a favorable exploration direction for Permian high-over mature gas fields(reservoirs). Great attentions should be paid to two types of targets, the deeply–buried structures and structural-lithologic traps. Based on three main gas systems, gas exploration is suggested be strengthened within three fields and on three levels.

Formation mechanism of condensates, waxy and heavy oils in the southern margin of Junggar Basin, NW China

It is a challenge to determine the source and genetic relationship of condensate, waxy and heavy oils in one given complicated petroliferous area, where developed multiple sets of source rocks with different maturity and various chemical features.The central part of southern margin of Junggar Basin, NW China is such an example where there are condensates, light oils, normal density oils, heavy crude oils and natural gases. The formation mechanism of condensates has been seriously debated for long time;however, no study has integrated it with genetic types of waxy and heavy oils. Taking the central part of southern margin of Junggar Basin as a case, this study employs geological and geochemical methods to determine the formation mechanism of condensates,waxy and heavy oils in a complicated petroliferous area, and reveals the causes and geochemical processes of the co-occurrence of different types of crude oils in this region. Based on detailed geochemical analyses of more than 40 normal crude oils, light oils,condensates and heavy oils, it is found that the condensates are dominated by low carbon number n-alkanes and enriched in light naphthenics and aromatic hydrocarbons. Heptane values of these condensates range from 19% to 21%, isoheptane values from1.9 to 2.1, and toluene/n-heptane ratios from 1.5 to 2.0. The distribution of n-alkanes in the condensates presents a mirror image with high density waxy crude oils and heavy oils. Combined with the oil and gas-source correlations of the crude oils, condensates and natural gas, it is found that the condensates are product of evaporative fractionation and/or phase-controlled fractionation of reservoir crude oils which were derived from mature Cretaceous lacustrine source rocks in the relatively early stage. The waxy oils are the intermediate products of evaporative fractionation and/or phase-controlled fractionation of reservoir crude oils, while the heavy oils are in-situ residuals. Therefore, evaporative fractionation and/or phase-controlled fractionation would account for the formation of the condensate, light oil, waxy oil and heavy oil in the central part of southern margin of Junggar Basin, resulting in a great change of the content in terms of light alkanes, naphthenics and aromatics in condensates, followed by great uncertainties of toluene/n-heptane ratios due to migration and re-accumulation. The results suggest that the origin of the condensate cannot be simply concluded by its ratios of toluene/n-heptane and n-heptane/methylcyclohexane on the Thompson's cross-plot, it should be comprehensively determined by the aspects of geological background, thermal history of source rocks and petroleum generation,physical and chemical features of various crude oils and natural gas, vertical and lateral distribution of various crude oils in the study area.

Double Difference Location of the Mainshock and Aftershocks of the Hutubi MS6.2 Earthquake That Occurred on December 8,2016

The mainshock and aftershocks of the Hutubi M_S6.2 earthquake on December 8,2016 were relocated by applying the double difference method, and we relocated 477 earthquakes in the Hutubi region. The earthquake relocation results show that the aftershocks are distributed in the east-west direction towards the north side of the southern margin of the Junggar Basin fault,and are mainly distributed in the western region of the mainshock. The distance between the mainshock after relocation and the southern margin of the Junggar Basin fault is obviously shortened. Combined with the focal mechanism and the spatial distribution of the mainshock and aftershocks,it is inferred that the southern margin of the Junggar Basin fault is the main seismogenic structure of the Hutubi earthquake.

准噶尔盆地南缘侏罗系八道湾组富藻类体煤系源岩的发现及其沉积背景

通过沉积有机质中生物标志化合物组合分析,并结合荧光显微组分镜检结果,本研究首次在准噶尔盆地南缘建功剖面下侏罗统八道湾组上段识别出一套富藻类有机质输入的煤系沉积。该套煤系源岩主体处于低成熟–成熟早期演化阶段,镜质组反射率为0.5%~0.6%;有机碳(TOC)含量主要介于2.0%~4.0%之间,局部发育碳质泥岩和煤线;生烃潜量(S_(1)+S_(2))值普遍为3.0~5.0 mg/g,碳质泥岩段最高达18.4 mg/g;氢指数(HI)主要为100~150 mg/g,碳质泥岩段达280 mg/g,属于Ⅱ2型有机质。沉积有机质中生物标志化合物组合表现为姥鲛烷优势,中、短链正构烷烃含量较高,C_(27)~C_(29)规则甾烷呈“V”型分布,Ts、C_(29)Ts、C_(30)H藿烷含量较高,C同位素组成较轻。全岩荧光显微镜镜检结果表明,源岩中壳质组主要为孢子体和藻类(屑)体。结合沉积背景综合判断,该套富藻类体煤系沉积形成于水体较深的湖泊沼泽化早期阶段,浮游藻类等低等水生生物对沉积有机质存在显著贡献,有望成为区域潜在的优质烃源岩。

基于离散元数值模拟的构造变形机制分析方法——以准噶尔盆地南缘为例

受多期构造运动影响,准噶尔盆地南缘前陆冲断褶皱带具横向东西分段、南北分带,纵向构造叠置的变形特征。但该区构造变形机制及样式的不同认识在一定程度上制约了油气勘探的深入。为探究准南缘新生代以来构造变形机制及其变形过程,本文利用高精度地震、钻井和岩石力学等资料,根据实际地质条件,重点考虑滑脱层的数量、强度及厚度变化,结合滑脱层纵向组合、横向分布范围及同沉积作用、先存构造等因素,共设计了10组模型,并采用离散元数值模拟方法开展了对比实验。实验结果表明,滑脱层强度、厚度及其组合主要控制冲断褶皱带构造纵向叠置关系及构造样式,滑脱层分布及同沉积作用主要控制其横向变形范围,先存构造主要影响后期构造的继承性发育。在此基础上,分段开展了多因素组合模拟实验并与实际地震剖面进行对比,重构了准南缘构造变形过程,揭示了新生代以来其构造变形机制,即先存断裂、古凸起、三套不同性质滑脱层纵向叠置关系和同沉积作用共同控制了西段构造的形成与演化,“下强上弱”“下薄上厚”两套纵向叠置滑脱层控制了中段构造的形成与演化,先存断裂及单套较弱滑脱层控制了东段构造的形成与演化。该方法可为类似的复杂构造变形区提供参考。

低程度风化火山岩风化壳结构划分与主控因素——以准噶尔盆地西缘车排子凸起石炭系火山岩为例

为解决低风化程度的火山岩风化壳结构划分及火山岩油气储层评价与预测的难题,利用研究区28口井岩心、录井测井和地震资料,对车排子凸起石炭系火山岩风化壳的岩石学、矿物学、地球化学、储层物性进行系统研究。结果表明:研究区岩石整体风化程度偏低。在此基础上提出一种将风化壳自上而下分为土壤带、水解带、淋滤带、崩解带、蚀变带、母岩带的6层划分方案。利用研究区玄武安山岩的自然电位、自然伽马、声波、电阻率4种测井数据,结合过采样算法的决策树模型对淋滤带、崩解带、蚀变带进行分类判别,准确率达87.8%。综合分析认为:低风化程度火山岩风化壳有效储层厚度、结构带发育程度、横纵向分布等具有非均质性;有利储层发育主要受古地貌和断裂作用的控制,淋滤带、崩解带是主要有利储层发育区,常分布于古地貌的斜坡地带,一般厚度在350 m以内;受断裂作用影响,风化壳有效储层厚度可达450 m。

埋藏过程对深层-超深层碎屑岩成岩作用及优质储层发育的影响——以准噶尔盆地南缘下白垩统清水河组为例

以准噶尔盆地南缘下白垩统清水河组为例,综合利用岩石薄片、扫描电镜、电子探针、稳定同位素组成及流体包裹体等技术手段,开展前陆盆地埋藏过程对深层—超深层碎屑岩成岩作用及优质储层发育影响的研究。研究表明,清水河组依次经历了“缓慢浅埋”、“构造抬升”、“渐进深埋”与“快速深埋”4个埋藏阶段。“缓慢浅埋”与“构造抬升”不仅能够缓解储层颗粒间的机械压实作用,还有利于长期保持开放型的成岩体系;既能够促进大气淡水对储层易溶组分的充分溶解,还能够抑制溶蚀产物的沉淀。晚期“快速深埋”过程促成流体超压的发育,一方面有效地抑制压实、胶结作用对原生孔隙的破坏,另一方面也促进储层微裂缝的大量发育,提高了晚期有机酸充注产生的溶蚀效果。基于孔隙度演化史的定量恢复,证实长期“缓慢浅埋”与“构造抬升”过程对深层—超深层优质碎屑岩储层发育的贡献最大,其次为晚期“快速深埋”过程,“渐进深埋”过程则几乎没有贡献。

准噶尔盆地南缘下侏罗统三工河组地球化学、沉积环境及源区特征分析

准噶尔盆地南缘是重要的油气勘探地区,也是研究盆地构造属性、沉积环境演化的重要区域。南缘下侏罗统三工河组由上部主体浅青灰色-灰绿色长石岩屑砂岩、粉砂质泥岩、泥质粉砂岩和下部土黄色长石岩屑砂岩、含砾粗砂岩、砾岩组成,对上部样品进行岩石学、岩相学和地球化学研究显示:样品化学蚀变指数(CIA)为77.57,反映物源区经历中等风化作用;碎屑物质磨圆和分选较差,表明沉积物搬运距离短,成分成熟度低;Cu/Zn、V/Cr、V/(V+Ni)、Ni/Co及U/Th值指示古沉积环境为富氧的氧化环境-贫氧过渡环境;Sr/Cu、Al_(2)O_(3)/MgO值指示温暖湿润的气候特征;Li,Sr,Sr/Ba,Th/U值指示淡水环境;综合岩相学特征认为,其上部主体为浅湖亚相沉积,下部为辫状河三角洲平原亚相沉积。样品中含流纹岩岩屑,La/Th-Hf、La/Sc-Co/Th和Ni-TiO_(2)判别图指示三工河组源岩主要来自于上地壳长英质火山岩;出现少量安山岩岩屑和Th/Co、Th/Cr比值显示源岩有少量中-基性岩。通过样品与不同构造背景杂砂岩成分对比、Th-Co-Zr/10、La-Th-Sc、Th-Sc-Zr/10判别图显示物源区应为大陆岛弧构造背景。

准噶尔盆地南缘西段齐古组深层储层特征及物性控制因素

准噶尔盆地南缘西段齐古组深层碎屑岩储层油气勘探潜力巨大,但目前针对其储层特征及物性控制因素尚缺乏系统研究,制约了后期油气勘探进程。本文综合利用铸体薄片、扫描电镜、物性、压汞及包裹体等资料,并结合区域埋藏史及古地温等相关成果,对齐古组储层岩石学特征、物性特征、成岩作用特征及物性控制因素进行系统研究。结果表明,齐古组储层具有低成分成熟度、高塑性岩屑含量及中等结构成熟度的岩石学特征。尽管储层主体埋深大于3500 m,但储集空间仍以粒间孔为主,平均孔隙度为10.29%,平均渗透率为34.12×10^(-3)μm^(2),总体上属低孔低渗储层,但仍发育部分中-高孔渗储层。储层成岩作用主要有压实作用、胶结作用及溶蚀作用,成岩强度相对较弱,主体处于早成岩B期—中成岩A期,并表现为压实强度中等、胶结物含量较低且晚期发育酸性溶蚀的特征。富石英与长石、贫岩屑以及分选好等特征有利于储层物性的保存,而储层物性损失以压实减孔最为显著,但储层内部绿泥石包壳及中成岩期的酸性溶蚀作用可有效改善储层物性。此外,齐古组地层早期长期浅埋、后期短期快速深埋、地层超压及较低的古地温梯度等因素延缓了储层成岩进程,进而降低成岩作用强度,导致齐古组优质储层得以有效保存。

基于核磁共振动态截止值理论的致密砂砾岩储层渗透率评价方法

准噶尔盆地南缘深层清水河组致密砂砾岩储层为该区的重要勘探领域,渗透率是评价致密砂砾岩储层的关键参数。为提高此类储层渗透率计算精度,基于核磁共振实验,分析致密砂砾岩岩心饱和水及离心核磁共振横向弛豫时间(T_(2))谱,明确致密砂砾岩孔隙中流体的赋存形态及渗流规律,提出常规核磁共振渗透率计算方法的不足,并且提出核磁共振动态截止值的概念。基于核磁共振动态截止值,将储层孔隙空间划分为3类:自由流体孔、毛细管半束缚孔、完全束缚孔;分析了渗透率与不同孔隙类型之间的相关关系:致密砂砾岩储层渗透率与自由流体孔孔隙度、核磁总孔隙度、毛细管半束缚孔的T_(2)几何平均值呈正相关关系,与完全束缚孔流体饱和度呈负相关关系。构建基于不同孔隙类型渗透率模型,计算渗透率与岩心实验渗透率之间的相对误差小于9.0%。该方法提高了致密砂砾岩储层渗透率的计算精度,且在准噶尔盆地南缘深层清水河组致密砂砾岩储层评价中具有广泛的应用前景。

超大井眼疏松地层声波时差采集与提取方法

在准噶尔盆地南缘山前超深层油气勘探中,由于声波能量受表层超大井眼、疏松地层衰减的影响,无法有效获取纵波时差。为解决此难题,对相关声波时差测井采集与提取方法进行了研究。针对超大井眼声波测井采集,提出了一种声波偏心仪器的测井方法,并选取偶极子阵列声波测井作为疏松地层声波测井系列。基于慢度-时间相关法提取声波时差的原理,利用频率开窗技术,锁定了区域偶极子声源激发的漏能纵波的频率为2.6~3.6 kHz;通过对横波信号与直达波信号进行频率过滤,确定了波形窗口、时差搜寻窗长和时差搜索偏移量处理参数,使得纵波信号最强,并将漏能纵波从偶极横波原始波形中分离出来,从而提取疏松地层的声波时差。应用该方法成功采集了准噶尔盆地南缘山前表层超大井眼、疏松地层12口井的偶极子声波资料,并提取了纵波时差。将提取的纵波时差应用于井震成像,显著提高了地震处理资料品质,为认识山前超深层构造和井位部署提供了重要依据。

准南西段清水河组底部砂砾岩体成因机制及发育模式

准南清水河组底部砂砾岩段油气勘探获重大突破,但砂砾岩的沉积特征、成因机制和发育控制因素仍不明确,成为制约下一步油气勘探的关键。以准南西段清水河组下段砂砾岩体为研究对象,运用沉积学理论,结合测井、录井、岩心、野外露头及实验分析数据,对砂砾岩体的岩相、岩相组合及沉积展布进行分析,并探讨砂砾岩体沉积发育的主控因素及成因机制。研究表明,准南西段清水河组低位及湖侵域识别出6种岩相及6种岩相组合类型。不同部位砂砾岩成因类型不同,西段南部高泉地区清水河组低位及湖侵域以冲积扇—扇三角洲沉积体系为主,北部卡因迪克地区以辫状河三角洲沉积为主。清水河组沉积期准南西段砂砾岩沉积受源区母岩性质、供源强度及古气候影响,其中,物源区母岩性质及供源强度控制砂砾岩体的沉积类型及规模,古气候影响母岩区风化剥蚀程度及沉积搬运环境。结合控制因素和沉积特征建立准南西段清水河组低位及湖侵域的南部冲积扇—扇三角洲及北部辫状河三角洲前缘的沉积发育模式,可为砂砾岩体的成因判别以及类似盆地的油气勘探提供地质依据。

准噶尔盆地南缘西部山前褶皱—冲断带构造分带特征及形成演化

准噶尔盆地南缘西部构造呈新的构造叠置特征和复杂的复合叠加构造样式,叠加构造在空间分布上具有明显的分带特征。根据野外地质调查和地震解释资料,采用平衡剖面恢复、楔型构造理论和构造地质学分析方法,研究复杂叠加构造变形差异及分带特征。结果表明:准噶尔盆地南缘西部发育受基底卷入与顺层滑脱联合与差异控制下的空间断褶体系,褶皱发育受断层控制,褶皱与断层相互叠加形成构造楔、双重构造、突发构造等复合构造样式,表现为多期活动特征。研究区按构造变形性质及变形差异可划分为山前逆冲推覆构造带、基底卷入型褶皱—冲断带、盖层滑脱型褶皱—冲断带3个构造带;其中,基底卷入型褶皱—冲断带与第一排断褶带重合,受控于基底卷入型断裂体系,发育基底卷入式大型构造楔、背形堆垛式双重构造与前倾双重构造,背斜轴线与断层线平面重合度高;盖层滑脱型褶皱—冲断带包括第二和第三排断褶带,受控于顺层滑脱型断裂体系,发育断展褶皱,背斜轴线与断层线平面重合度低,构造垂向上具有分层差异,构造变形程度自南向北表现为由强至弱。挤压应力作用的时期和强度、滑脱断层的向北滑脱、构造楔的楔入长度及推挤距离、滑脱层的厚度和上覆地层厚度,以及沉积时代、沉积速率和岩性差异等因素是引起研究区构造垂向分层、南北分带的原因。该结果对明确研究区构造发育及下一步油气地质勘探具有指导意义。

超深高压砂岩气藏临界出砂压差预测

超深高压高产气藏开采过程中往往会面临严重的储层出砂问题,出砂会使砂埋井眼、冲蚀井下油套管柱和地面设备、造成气井减产甚至停产,严重时会导致气井报废。由于高地应力(高水平主应力差)、裂缝发育,气体流速较快等原因,超深高压气井出砂预测困难,常规油气井出砂预测方法适用性不强。以准噶尔盆地南缘区块高压高产砂岩气藏为研究对象,采用理论模型推导分析、数值模拟等手段重点开展高压高产气井出砂影响因素分析及预测方法研究。建立了超深高压气井射孔完井临界出砂压差预测模型,开展了模型适应性评价,验证了其预测精度。研究成果对后续南缘区块高压、高产气井制定安全生产制度具有重要指导意义。