Numerical Simulation Study on the Effect of Horizontal Well Reservoir Stimulation for Gas Hydrate Production

A new gas hydrate reservoir stimulation method of in-situ fracturing with transient heating is proposed, in line with analysis of the technological bottlenecks faced by marine gas hydrate production. This method injects the developed chemical reagents into a hydrate reservoir through hydraulic fracturing, releasing heat during the chemical reaction to increase the hydrate decomposition rate. The chemical reaction product furthermore has a honeycomb structure to support fractures and increase reservoir permeability. Based on the geological model of natural gas hydrate in the South China Sea, three development methods are simulated to evaluate hydrate production capacity, consisting of horizontal well, fractured horizontal well and in-situ fracturing with transient heating well. Compared with the horizontal well, the simulation results show that the cumulative gas production of the fractured horizontal well in one year is 7 times that of the horizontal well, while the cumulative gas production of in-situ fracturing with transient heating well is 12 times that of the horizontal well, which significantly improves daily efficiency and cumulative gas production. In addition, the variation patterns of hydrate saturation and temperature-pressure fields with production time for the three exploitation plans are presented, it being found that three sensitive parameters of fracture conductivity, fracture half-length and fracture number are positively correlated with hydrate production enhancement. Through the simulations, basic data and theoretical support for the optimization of gas hydrate reservoir stimulation scheme has been provided.     

纪念李世雄教授去世一周年

在李世雄教授去世一周年之际,本文以笔者工作的领域为例,阐述他近20年来通过李群和李代数、微局部分析、调和分析、小波分析、独立分量分析方面的基础研究,为保结构方法在地震成像研究中的引入、反假频高频重建在储层预测中的引入作出的重要贡献.从而表达对李世雄教授的高尚人品和精妙学术教学水平的由衷敬佩.     

Episodic fluid movements in superimposed basin:Combined evidence from outcrop and fluid inclusions of the Majiang ancient oil reservoir,Guizhou Province

Combined evidence from the outcrop and the fluid inclusion assemblage (FIA) analysis indicates that there exist two episodes of fluid flow controlled by the tectonic activity. The first episode was recorded mainly in the reservoir rock of the Honghuayuan Formation,representing the fluid flow of hydrocarbon charging. The second episode occurred mainly along the fault systems,representing the fluid move-ment when the ancient oil reservoir was destroyed. The host mineral morphology,homogeneous tem-perature,and salinity of the FIAs record an episodic fluid movement. Characters of high homogenous temperature,low salinity and a quick temperature variation of the first episode fluid flow may indicate an early-stage fluid eruption,and correspondingly,fine-grained calcite was formed. Temperature of the erupted fluid tended to decrease during its mixing with the upper formation fluid and finally had the same temperature as the upper formation. From then on,the temperature was rather steady and fa-vored the growth of the coarse calcite. Due to this character of the temperature variation of the episodic fluid flow,we can use the homogenous temperature of the FIA of the coarse calcite to date the forma-tion and the destruction time of the Majiang ancient oil reservoir. Episodic fluid flow was known for its inhomogeneous trapping,which resulted in the failure of dating according to the burial history. But taking a close look at its temperature variation,we think that the latest stage of fluid flow,characterized by steady state temperature and grow of the coarser crystals,can be used for dating. It will be of great value if this method is proved to be effective. The formation and the destruction time of the Majiang ancient oil reservoir were dated to be in the Indosinian Period and the late Yanshan-early Hymalayan Period respectively. This conclusion is in great discrepancy with the common accepted idea that the Majiang ancient oil reservoir was formed and destroyed during the Caledonian tectonic movement. Even so,this paper further discussed its reliability from the view of the source rock evolution and also the local tectonic evolution.     

The distribution rule and seepage effect of the fractures in the ultra-low permeability sandstone reservoir in east Gansu Province,Ordos Basin

To study the impact of the fractures on development in the ultra-low permeability sandstone reservoir of the Yangchang Formation of the Upper Triassic in the Ordos Basin,data on outcrops,cores,slices,well logging and experiments are utilized to analyze the cause of the formation of the fractures,their distribution rules and the control factors and discuss the seepage flow effect of the fractures. In the studied area developed chiefly high-angle tectonic fractures and horizontal bedding fractures,inter-granular fractures and grain boundary fractures as well. Grain boundary fractures and intragranular fractures serve as vital channels linking intragranular pores and intergranular solution pores in the reservoir matrix,thus providing a good connectivity between the pores in the ultra-low perme-ability sandstone reservoir. The formation of fractures and their distribution are influenced by such external and internal factors as the palaeo-tectonic stress field,the reservoir lithological character,the thickness of the rock layer and the anisotropy of a layer. The present-day stress field influences the preservative state of fractures and their seepage flow effect. Under the tec-tonic effect of both the Yanshan and Himalayan periods,in this region four sets of fractures are distributed,respectively assuming the NE-SW,NW-SE,nearly E-W and nearly S-N orientations,but,due to the effect of the rock anisotropy of the rock formation,in some part of it two groups of nearly orthogonal fractures are chiefly distributed. Under the effect of the present-day stress field,the fractures that assume the NE-SW direction have a good connectivity,big apertures,a high permeability and a minimum starting pressure,all of which are main advantages of the seepage fractures in this region. With the development of oilfields,the permeability of the fractures of dif-ferent directions will have a dynamic change.     

Analyzing spatial ecological data using linear regression and wavelet analysis

Spatial (two-dimensional) distributions in ecology are often influenced by spatial autocorrelation. In standard regression models, however, observations are assumed to be statistically independent. In this paper we present an alternative to other methods that allow for autocorrelation. We show that the theory of wavelets provides an efficient method to remove autocorrelations in regression models using data sampled on a regular grid. Wavelets are particularly suitable for data analysis without any prior knowledge of the underlying correlation structure. We illustrate our new method, called wavelet-revised model, by applying it to multiple regression for both normal linear models and logistic regression. Results are presented for computationally simulated data and real ecological data (distribution of species richness and distribution of the plant species Dianthus carthusianorum throughout Germany). These results are compared to those of generalized linear models and models based on generalized estimating equations. We recommend wavelet-revised models, in particular, as a method for logistic regression using large datasets.     

清江水布垭库区大堰塘滑坡涌浪分析

2007年6月15日位于水布垭水库巴东县清太平镇的大堰塘滑坡发生滑动,激起高达50 m的巨大涌浪,造成了沿岸的人员伤亡。为了解决大堰塘滑坡引起的涌浪问题,把滑坡引起的涌浪分为体积涌浪和冲击涌浪两部分。根据体积守恒原理及块体水下运动的位移公式求出了初始涌浪的计算公式。把滑坡涌浪衰减过程分为急剧衰减和缓慢衰减两个阶段来考虑,并认为急剧衰减阶段的涌浪的衰减符合指数衰减规律,缓慢衰减阶段符合明槽水流的沿程水头损失规律,对其涌浪的传播和爬坡进行了深入探讨,并与实际调查结果进行了对比分析,该成果对水库库岸滑坡的涌浪传播的研究具有一定的参考意义。     

松辽盆地朝长地区扶余油层的构造演化

扶余油层是松辽盆地朝长地区开发的主要目的层段,确定其幕式构造运动期次及其构造变形历史,对于圈闭形成演化、油气成藏分析以及外扩挖潜均具有十分重要的现实意义。通过构造发育史剖面图和古构造图编制,确定朝长地区扶余油层的幕式构造运动期次和构造变形特征。研究表明,朝长地区泉头组扶余油层自沉积开始至嫩江组沉积期为统一的坳陷区,其后经历了嫩江期末、明水期末、古近纪末3个主要的幕式构造运动期次。朝长地区的构造变形总体呈现东强西弱、南强北弱的特点。嫩江晚期至期末在朝长地区东南部形成构造雏形;明水期末形成构造幅度较高的长春岭背斜带和低幅度的朝阳沟阶地;古近纪末长春岭背斜带定型,发育长春岭、三站和五站背斜,而定型的朝阳沟阶地由朝阳沟背斜、翻身屯背斜等组成。     

大港滩海地区石油地质特征及勘探潜力

大港滩海地区地处渤海湾盆地腹地,位于黄骅裂谷盆地东侧海岸线以东水深5 m线的地区,是古近纪以来发育形成的凹隆相间的复合构造区。该区自上而下发育4套生油层系,即东二段、沙一中段、沙二段、沙三段;储层发育,冲积扇、水下扇、三角洲、扇三角洲、辫状河三角洲、重力流、湖泊碳酸盐岩在滩海区广泛分布;8个二级正向构造带呈近东西向和北东南西向分布在凹陷之间,具有形成大-中型油气藏的先决条件。通过对工区地层、储层、构造、生油、成藏等石油地质条件的分析,阐述了油藏的成藏条件及油气富集规律;通过对各区带的地质条件和勘探开发现状分析,指出其油气勘探开发潜力。认为滩海地区虽然地表地下条件复杂、对勘探开发技术要求高、勘探开发成本高、风险大,但滩海区油气资源量大,成藏条件好,目前勘探开发程度低,是大港油田今后增储上产的现实领域。     

特低渗透裂缝型储层注水开发中后期地应力场变化及开发对策

从特低渗透裂缝型储层油田开发实践中暴露出来的问题入手,从理论上研究了注水开发中后期地下储层水平应力场“均一化”的发展趋势,认为注水开发中后期井区局部视水平最小主应力,随着注水开发周期的延长将会无限接近水平最大主应力。在此基础上描述了特低渗透储层发育天然裂缝和不发育天然裂缝时注入水的流动规律。最后根据水平应力场注水开发中后期“均一化”理论,提出针对特低渗透裂缝储层注水开发中后期的调整对策。此项技术在大庆头台油田茂11区块进行应用,取得了比较好的调整效果,并对同类油田开发具有重要指导作用。     

川口油田长6储层成岩作用

详细分析了川口油田长6储层的成岩作用类型、储层物性演化及影响因素。通过岩石学、铸体薄片、电镜扫描等研究方法说明川口油田长6储层主要成岩作用包括压实-压溶作用、胶结作用、交代蚀变作用及溶蚀作用等,成岩阶段属晚成岩A期。其中,机械压实作用、化学胶结作用是导致砂岩孔隙度降低、储集性能变差的主要因素。机械压实作用主要表现为软碎屑的塑性变形、颗粒间由点接触向凹凸接触演变;胶结作用表现为浊沸石、绿泥石、粘土矿物、碳酸盐胶结;石英和长石的次生加大、溶蚀作用特别是浊沸石的溶蚀在一定程度上提高和改善了砂岩储集性能。结果表明,影响储层物性的主要因素为沉积作用和成岩作用。