Pressure transient analysis of a finite-conductivity multiple fractured horizontal well in linear composite gas reservoirs

Faulted gas reservoirs are very common in reality,where some linear leaky faults divide the gas reservoir into several reservoir regions with distinct physical properties.This kind of gas reservoirs is also known as linear composite(LC)gas reservoirs.Although some analytical/semi-analytical models have been proposed to investigate pressure behaviors of producing wells in LC reservoirs based on the linear composite ideas,almost all of them focus on vertical wells and studies on multiple fractured horizontal wells are rare.After the pressure wave arrives at the leaky fault,pressure behaviors of multiple fractured horizontal wells will be affected by the leaky faults.Understanding the effect of leaky faults on pressure behaviors of multiple fractured horizontal wells is critical to the development design.Therefore,a semi-analytical model of finite-conductivity multiple fractured horizontal(FCMFH)wells in LC gas reservoirs is established based on Laplace-space superposition principle and fracture discrete method.The proposed model is validated against commercial numerical simulator.Type curves are obtained to study pressure characteristics and identify flow regimes.The effects of some parameters on type curves are discussed.The proposed model will have a profound effect on developing analytical/semi-analytical models for other complex well types in LC gas reservoirs.

A multilevel preconditioner and its shared memory implementation for a new generation reservoir simulator

As a result of the interplay between advances in computer hardware, software, and algorithm, we are now in a new era of large-scale reservoir simulation, which focuses on accurate flow description, fine reservoir characterization, efficient nonlinear/linear solvers, and parallel implementation. In this paper, we discuss a multilevel preconditioner in a new-generation simulator and its implementation on multicore computers. This preconditioner relies on the method of subspace corrections to solve large-scale linear systems arising from fully implicit methods in reservoir simulations. We investigate the parallel efficiency and robustness of the proposed method by applying it to million-cell benchmark problems.

Derivation of Multipurpose Single Reservoir Release Policies with Fuzzy Constraints

Recent research modeling uncertainty in water resource systems has highlighted the use of fuzzy logic based approaches. The uncertainties in water resource systems include fuzziness, subjectivity, imprecision and lack of adequate data. In this paper we focus on Fuzzy Linear Programming (FLP) problem for reservoir opera- tion with fuzzy objectives function and fuzzy constraints. Uncertainty in reservoir operation parameters such as reservoir storages, releases for irrigation, releases for hydropower production, irrigation demands, and power demands are considered by treating them as a fuzzy set. This study is devoted to the identification of optimal operating policy using three different models. A fuzzy linear programming reservoir operation models are developed within a linear programming framework. These models are applied to a case study of Jayakwadi reservoir stage -II, Maharashtra State, India with the objective of maximization of releases for irrigation and hydropower. Fuzzy set theory is used to model imprecision in various parameters by developing three models. First model considers fuzzy resources, second model is with fuzzy technological coefficients and third model considers both, fuzzy technological coefficients and fuzzy resources in linear programming framework. Fuzziness in objective function and in the constraints is quantified by a membership functions. These three models are solved to obtain compromise solution by simultaneously optimizing the fuzzified objectives and constraints. The degree of satisfaction is obtained by simultaneously optimizing the objectives are 0.53, 0.52 and 0.525 by three models respectively. The obtained result show that proposed methodology provides an effective and useful tool for reservoir operation where decision maker can decides to opt for a model depends on the imprecision involved in reservoir operation model parameters.

Elastic modulus extraction based on generalized pre-stack PP–PS wave joint linear inversion

Joint PP–PS inversion offers better accuracy and resolution than conventional P-wave inversion. P-and S-wave elastic moduli determined through data inversions are key parameters for reservoir evaluation and fluid characterization. In this paper, starting with the exact Zoeppritz equation that relates P-and S-wave moduli, a coefficient that describes the reflections of P-and converted waves is established. This method effectively avoids error introduced by approximations or indirect calculations, thus improving the accuracy of the inversion results. Considering that the inversion problem is ill-posed and that the forward operator is nonlinear, prior constraints on the model parameters and modified low-frequency constraints are also introduced to the objective function to make the problem more tractable. This modified objective function is solved over many iterations to continuously optimize the background values of the velocity ratio, which increases the stability of the inversion process. Tests of various models show that the method effectively improves the accuracy and stability of extracting P and S-wave moduli from underdetermined data. This method can be applied to provide inferences for reservoir exploration and fluid extraction.

Multi-Reservoir Optimization for Maximization of Releases for Hydropower Generation Considering Environmental Flow

Water is the soul of the world. It is the most important element for the survival of humans, animals, birds, plants and all other living things on earth. Water is essential for the beginning of life as well as regular availability of water ensuring the survival, growth and overall nourishment. Thus, proper planning and use of reservoir water are essential for all. To tackle this issue different optimization techniques underline their need and importance in the reservoir operations. In the present study, multi-reservoir optimization model is developed using Python programing language considering the objective of maximization of total annual release for hydropower generation. Model is applied to 3 reservoirs from Godavari River basin from Maharashtra state India. Water essential for conservation of environment has also been made available in river as environmental flow as per the recommendations of Central Water Commission (CWC) India. Developed optimization model provides optimal monthly operation policies.

Sustainable Multi-Objective Multi-Reservoir Optimization Considering Environmental Flow

Increasing demand for water from all sectors presents a challenge for policy makers to improve water allocation policies for storage reservoirs. In addition, there are many other organisms and species present in river waters that also require water for their survival. Due to the lack of awareness many times the minimum required quantity and quality of water for river ecosystem is not made available at downstream of storage reservoirs. So, a sustainable approach is required in reservoir operations to maintain the river ecosystem with environmental flow while meeting the other demands. Multi-objective, multi-reservoir operation model developed with Python programming using Fuzzy Linear Programing method incorporating environmental flow requirement of river is presented in this paper. Objective of maximization of irrigation release is considered for first run. In second run maximization of releases for hydropower generation is considered as objective. Further both objectives are fuzzified by incorporating linear membership function and solved to maximize fuzzified objective function simultaneously by maximizing satisfaction level indicator (λ). The optimal reservoir operation policy is presented considering constraints including Irrigation release, Turbine release, Reservoir storage, Environmental flow release and hydrologic continuity. Model applied for multi-reservoir system consists of four reservoirs, i.e., Jayakwadi Stage-I Reservoir (R1), Jayakwadi Stage-II Reservoir (R2), Yeldari Reservoir (R3), Siddheshwar Reservoir (R4) in Godavari River sub-basin from Marathwada region of Maharashtra State, India.

Optimal Irrigation Planning and Operation of Multi Objective Reservoir Using Fuzzy Logic

In the present study the MOFLP models have been developed for the optimal cropping pattern planning which maximizes the four objectives such as Net Benefits (NB), Crop Production (CP), Employment Generation (EG) and Manure Utilization (MU) under conflicting situation and also, for maximization of Releases for Irrigation (RI) and Releases for Power (RP) simultaneously under uncertainty by considering the fuzziness in the objective functions. The developed models have been applied using the LINGO 13 (Language for Interactive General Optimization) optimization software to the case study of the Jayakwadi Project Stage-II across Sindhphana River, in the State of Maharashtra India. The various constraints have been taken into consideration like sowing area, affinity to crop, labour availability, manure availability, water availability for optimal cropping pattern planning. Similarly constraints to find the optimal reservoir operating policy are releases for power and turbine capacity, irrigation demand, reservoir storage capacity, reservoir storage continuity. The level of satisfaction for a compromised solution of optimal cropping pattern planning for four conflicting objectives under fuzzy environment is worked out to be λ = 0.68. The MOFLP compromised solution provides NB = 1088.46 (Million Rupees), CP = 241003 (Tons), EG = 23.13 (Million Man days) and MU = 111454.70 (Tons) respectively. The compromised solution for optimal operation of multi objective reservoir yields the level of satisfaction (λ) = 0.533 for maximizing the releases for irrigation and power simultaneously by satisfying the constraint of the system under consideration. The compromised solution provides the optimal releases, i.e. RI = 348.670 Mm3 and RP = 234.285 Mm3 respectively.

基于MLR–ANN算法的地应力场反演与裂缝预测

中国页岩气储层埋藏深,受构造运动影响,地应力分布规律复杂,传统方法很难准确反演区域地应力大小和方向。提出多元线性回归和人工神经网络的耦合算法,对川南长宁—建武区块的页岩气储层及周边地应力场进行反演,并采用综合破裂系数法,对储层裂缝进行预测,划分裂缝发育区域。研究表明,基于多元回归和神经网络的耦合算法能准确反演区域的地应力场分布规律。研究区的地应力以挤压应力为主,方向在NE115°左右。受构造运动产生的断层周边应力较为集中,易发育剪切裂缝,裂缝以发育和较发育程度为主。研究区在邻近龙马溪组底部的五峰组上段和构造大断层部位裂缝发育程度较高。研究成果对该区块完善页岩气开采的井网布置、压裂优化设计和套管损坏防治等有一定的参考价值。

基于高斯混合模型的碳酸盐岩储层物性与孔隙参数地震岩石物理同步反演

碳酸盐岩储层是我国油气资源增储上产的重要领域,然而此类储层通常发育复杂的孔隙结构,极易影响物性参数地震预测结果的精度.本文提出一种基于高斯混合模型的物性与孔隙参数地震岩石物理同步反演方法.基于微分有效介质模型和Gassmann方程,推导定量关联孔隙度、流体饱和度及孔隙纵横比与弹性参数的线性正演算子.引入了高斯混合模型表征物性与孔隙参数的联合先验概率分布,进而表征岩相统计差异特征.基于贝叶斯线性反演理论及线性正演算子,构建目标参数后验概率的解析表达式,然后根据测井数据反演井旁孔隙纵横比,以提供可靠的孔隙参数先验约束,并利用迭代贝叶斯反演算法,提高线性正演算子的模拟精度.本方法将孔隙纵横比作为反演目标参数,表征碳酸盐岩孔隙结构的空间变化特征,结合贝叶斯线性反演方法,以提高物性参数地震反演结果的精度与运算效率.数据测试表明,所提出的方法物性参数反演结果对比常规方法精度有明显改善,且在一定程度上,新方法受初始模型和弹性参数的影响较小.三维地震数据的应用验证了本方法的有效性,其孔隙度反演结果能够有效的指示有利储层的空间分布.

裂缝性低渗油藏压裂水平井井网渗流数学模型

基于分形理论表征天然裂缝和压裂裂缝网络的复杂裂缝形态,针对裂缝性低渗透储层的非线性渗流特征和储层压敏特性,建立了裂缝性低渗透油藏压裂水平井-直井井组的非线性渗流模型。根据流体在混合井网中的不同流动形态,划分为3个区域,推导出了混合井网三区耦合产能公式,分析了分形维数、压敏效应、裂缝长度等参数对井网产能的影响。

利用简化曲线交会法初步确定HDPE土工膜厚度

采用曲线交会法确定平原水库库盘土工膜厚度时,存在材料特性曲线难获得、需多次读图取数、重复试验次数多、可选择性小等不便之处。为此,基于曲线交会法的基本原理和材料弹性阶段的线弹性与双曲线应力-应变本构关系,推导了初步确定高密度聚乙烯(HDPE)土工膜厚度的简化曲线交会法(包括简化线弹性法和简化双曲线法),并对新疆某平原水库HDPE土工膜厚度的选取进行了计算分析。结果表明:(1)与曲线交会法相比,简化曲线交会法计算误差较小,拉应力安全系数误差平均约为2.22%,应变安全系数误差平均约为-4.24%,说明该方法较为准确合理;(2)当其他条件相同时,正方形孔隙拉应力安全系数最低,以其为该工程安全运用的判断基准;(3)对同一孔隙条件,安全系数随土工膜厚度增加而增加,且呈近似线性关系;(4)通过计算得到满足安全系数要求的HDPE土工膜厚度范围为≥0.5 mm。简化曲线交会法有助于土工膜厚度确定时的便捷计算,可以满足工程设计阶段初步确定HDPE土工膜厚度的要求。

龙羊峡水库蓄丰补枯特征研究

丰、枯水期末蓄水量是影响多年调节水库蓄丰补枯规则的关键要素。以黄河上游龙羊峡水库为研究对象,基于该水库的历史运行资料,考虑水库丰、枯水期的来水量、初始蓄水量等影响,采用多元线性回归方程建立调度函数,推求丰、枯水期水库增补水量,确定水库的丰、枯水期末蓄水量。结果表明:(1)龙羊峡水库丰水期增水量的距平值与来水量的距平值呈显著的正相关性(R^(2)=0.42),枯水期水库补水量的距平值与初始蓄水量的距平值呈显著的正相关性(R^(2)=0.16);(2)由调度函数推求的丰水期增水量与实际增水量的相关性良好(R^(2)=0.62),枯水期补水量与实际补水量相关性也较好(R^(2)=0.38)。研究成果可为龙羊峡水库调度规则的建立提供依据,也可为其他多年调节水库的调度提供参考。

地下径流退水过程规律

地下径流退水过程是水文过程的重要组成部分.选择滦河水系2个子流域(柳河流域和瀑河流域)的几场地下径流的退水过程,通过图形分析初步确定了2个子流域地下径流的退水规律,计算了地下径流的退水常数.并通过模型模拟的方法计算了模型模拟的误差,比较了几种模型模拟结果的优劣.结果表明,柳河流域地下径流服从指数退水规律,瀑河流域地下径流服从线性水库退水规律,且不同的降雨类型对应的退水常数不同.研究流域的地下径流退水过程,可为流域洪水过程的基流分割和地下径流的汇流计算提供依据.

基于数字平台的黄河多沙粗沙区分布式水文模型研究——以黄河岔巴沟流域为例

本文以黄河无定河水系岔巴沟流域为例,针对其气候、植被以及下垫面条件等时空变化特征,在全流域1∶1万DEM基础上,建立了具有物理基础的分布式流域水文模型,模型由网格单元的超渗产流模型和汇流模型组成,提出了考虑流域水保措施的流域汇流计算。使用该模型对1970～1989年大中场次洪水进行模拟计算,结果表明:计算值与实测值基本吻合。

TOPKAPI模型的改进及其在淮河流域洪水模拟中的应用研究

TOPKAPI模型是一个以物理概念为基础的分布式流域水文模型。对TOPKAPI模型进行了改进,增加了植物截留、降水下渗、土壤水深层渗漏、地下径流、河川径流等计算模块,并对壤中流计算模块作了相应的调整,将TOPKAPI模型改进成为一个较完整的分布式流域水文模型。采用因特网(Internet)上免费提供的数字高程、土壤和植被类型等网格资料,选用流域面积约为10000km2的中国淮河息县以上流域,应用改进后的TOPKAPI模型进行了洪水模拟,模型成果令人满意。

裂缝性油藏流固耦合渗流

本文给出了考虑介质变形的双重孔隙介质流固耦合渗流模型 ,并考虑渗流参数随有效应力而变化的非线性双重孔隙介质流固耦合渗流。在此基础上 ,本文还推导了双重孔隙介质非线性流固耦合渗流有限元计算格式 ,编制了计算机程序。并可模拟单孔隙 ,双重孔隙 ,常系数线性和变系数非线性等流固耦合渗流计算。并给出了算例。

油藏储层中不同赋存状态烃类地球化学特征:Ⅰ链烷烃——以鄂尔多斯盆地三叠系延长组为例

通过对鄂尔多斯盆地西峰油田三叠系延长组六个油砂样品中游离烃、封闭烃、碳酸盐胶结物烃、束缚烃和石英颗粒包裹体烃的分步分离和抽提,并对每类烃的不同馏分进行GC-MS分析。根据所分析样品的成岩作用序列,结合样品的结构特征,表明这一方法是可行的。通过对不同赋存状态链烷烃的研究表明,研究区正构烷烃峰型为单峰型,碳数分布广,具较弱的奇碳优势。烃类的母质类型显示为Ⅰ—Ⅱ型干酪根,形成于开阔水体条件下还原的淡水湖相环境。Pr/Ph比值、CPI值,在不同赋存状态烃中差异比较明显,大体上从游离烃、封闭烃、胶结物烃、束缚烃到包裹体烃有减小的趋势。结合其族组分特征,反映了油气演化的阶段性及其成藏期次和油藏微观的不均一性。

河道洪水演算方法在淮河及滹沱河中游的应用

为解决马斯京根法在河道洪水演算中未考虑河道断面特征和水力特性的变化问题,在淮河中游吴家渡至小柳巷河段、滹沱河中游黄壁庄至北中山河段采用考虑河道断面几何形状和水力学糙率的Muskingum-Cunge-Todini可变参数法和非线性水库法进行河道洪水演算研究,探讨考虑河道断面特征和水力特性的演算方法在湿润区淮河中游及半干旱区滹沱河中游的适用性,并将模拟结果与马斯京根法进行比较。结果表明,Muskingum-Cunge-Todini可变参数法和非线性水库法在研究河道上模拟精度较高,洪峰合格率均在86%以上,确定性系数均大于0.8,可应用于河道洪水预报。

含水率与含水饱和度直线模型的物理意义及变化特征

为了系统论述含水率fw与含水饱和度Sw直线模型截距a、斜率b的物理意义,利用大量试验资料分析了a和b的变化特征,认为斜率b可以作为直线模型的特征参数。分析表明,斜率b值的变化受试验温度、油水流体性质、岩石物理性质等基本条件的影响,随着试验温度的升高、原油粘度增大、油水界面张力减小,以及储层渗透率的增大、孔隙结构的变好,b值是逐渐减小的。以此认识为基础建立直线模型系数的经验方程,可以方便地计算残余油饱和度、水驱油效率,并计算不同含水阶段的剩余可动油饱和度,有利于正确评价水淹层。

体积压裂页岩油储层渗流规律及产能模型

利用岩心实验,研究页岩油储层纳微米孔喉渗流规律.基于分形理论,采用双重分维(缝宽分维和迂曲分维),对体积压裂裂缝面密度、等效渗透率等参数进行表征.页岩油储层体积压裂开发过程中,流体的流动分为椭圆缝网内渗流区和主干缝内线性渗流区2个区域,建立二区耦合稳态渗流数学模型,推导页岩油体积压裂改造储层直井产能方程,模拟计算压裂井产能及分析压裂裂缝参数对产能的影响.结果表明:缝宽分形维数越大,裂缝面密度越大,基质—裂缝等效渗透率越大;当裂缝面密度较大时,增加储层改造宽度对产能提升有较大影响;次生缝导流能力越高,提高主干缝导流能力对产能影响越大,次生缝导流能力越小,影响越小.