Reservoir description using dynamic parameterisation selection with a combined stochastic and gradient search

There is a correspondence between flow in a reservoir and large scale permeability trends. This correspondence can be derived by constraining reservoir models using observed production data. One of the challenges in deriving the permeability distribution of a field using production data involves determination of the scale of resolution of the permeability. The Adaptive Multiscale Estimation (AME) seeks to overcome the problems related to choosing the resolution of the permeability field by a dynamic parameterisation selection. The standard AME uses a gradient algorithm in solving several optimisation problems with increasing permeability resolution. This paper presents a hybrid algorithm which combines a gradient search and a stochastic algorithm to improve the robustness of the dynamic parameterisation selection. At low dimension, we use the stochastic algorithm to generate several optimised models. We use information from all these produced models to find new optimal refinements, and start out new optimisations with several unequally suggested parameterisations. At higher dimensions we change to a gradient-type optimiser, where the initial solution is chosen from the ensemble of models suggested by the stochastic algorithm. The selection is based on a predefined criterion. We demonstrate the robustness of the hybrid algorithm on sample synthetic cases, which most of them were considered insolvable using the standard AME algorithm.     

Optimization of nonconventional wells under uncertainty using statistical proxies

The determination of the optimal type and placement of a nonconventional well in a heterogeneous reservoir represents a challenging optimization problem. This determination is significantly more complicated if uncertainty in the reservoir geology is included in the optimization. In this study, a genetic algorithm is applied to optimize the deployment of nonconventional wells. Geological uncertainty is accounted for by optimizing over multiple reservoir models (realizations) subject to a prescribed risk attitude. To reduce the excessive computational requirements of the base method, a new statistical proxy (which provides fast estimates of the objective function) based on cluster analysis is introduced into the optimization process. This proxy provides an estimate of the cumulative distribution function (CDF) of the scenario performance, which enables the quantification of proxy uncertainty. Knowledge of the proxy-based performance estimate in conjunction with the proxy CDF enables the systematic selection of the most appropriate scenarios for full simulation. Application of the overall method for the optimization of monobore and dual-lateral well placement demonstrates the performance of the hybrid optimization procedure. Specifically, it is shown that by simulating only 10% or 20% of the scenarios (as determined by application of the proxy), optimization results very close to those achieved by simulating all cases are obtained.     

Transparency: aid or obstacle to effective defence of vulnerable environments from reservoir construction? Dam decisions and democracy in North East England

Public participation in transparent decisionmaking has been proposed as a panacea for environmental protection. Bargaining theory suggests drawbacks to transparency such as hardening of attitudes and intransigence. Yet achievement of consensus on environmental values for integrated water resource management demands public involvement. Historical study of attempts to prevent reservoir construction in upland valleys designated for protection of nature suggests that 'closed-door' bargaining proved more effective for environmentalists than open, public debate. Records now open for analysis of disputes over Teesdale and Farndale, 1950–1970, allow comparisons to be made between behind-the-scenes deliberations and 'open-door' public discussion. The ambition of progressing from public participation to devolution of environmental decisionmaking and responsibility to the local scale demands more conceptualization of the process of decisionmaking on water resource development.     

Semi-Analytic Modelling of Subsidence

This paper presents a forward model for subsidence prediction caused by extraction of hydrocarbons. The model uses combinations of analytic solutions to the visco-elastic equations, which approximate the boundary conditions. There are only a few unknown parameters to be estimated, and, consequently, calculations are very fast. The semi-analytic model is applicable to a uniform and layer-cake stratigraphy, with visco-elastic parameters changing per layer, and an arbitrary depletion pattern. By its capabilities to handle a multi-layered visco-elastic subsurface, the semi-analytic model fills the gap between the analytic single-layered elastic models available to date and the more elaborate numerical, e.g. finite element, models.     

地震属性分析中水平切片的应用

利用地震数据体中含有的丰富地质信息,可以有效地进行储层预测。层拉平水平切片地层学解释方法是先将地震剖面目的层段做层拉平处理,然后对切片顺地层层面追踪,勾绘出各种地层现象,并以地层学的观点加以解释。该方法在吉林探区扶新南部地区的应用中,对于识别河道的展布趋势取得了较好的效果,而且发现了多期叠置的扇型沉积体。另外,还可指导反演数据体的解释,做到对岩性体从定性到定量的描述。     

台北凹陷中浅储集层孔隙预测及勘探有效下限探讨

在系统研究储层物性控制因素的基础上，分析台北凹陷中浅储集层物性分布规律以及压实程度特征，建立孔隙度一深度趋势法和压实减孔量法预测砂岩孔隙度．认为中侏罗统储层压实减孔量整体比较高，表现出“北高南低，生油凹陷内高、周边低”的特征．结合探井试油资料，确定侏罗系储集层有效下限的孔隙度值为9％，压实减孔量为34％，各构造带侏罗系储层深度有效下限总体上表现出“南深北浅、西深东浅”的特征．指出台北凹陷侏罗系储集层在有效下限以下勘探具有较大风险．     

舞阳、襄城盐湖盆地未熟-低熟油成藏模式

舞阳、襄城凹陷下第三生活费为膏、盐岩相盐湖沉积。半咸水-咸水湖相、盐湖相是形成未熟-低熟油的良好环境，沉积旋回中期断坳式沉积形成了主要油源层系，其高丰度未熟烃类推岩体是形成未熟-低熟油藏的物质基础，中-高孔、中-高渗碎屑岩层构成了未熟-低熟油藏的重要储集层，并发育了较好的生储盖组合，这些有利条件为舞阳、襄城凹陷形成未熟-低熟油藏提供了重要保证。指出凹陷陡坡带为背斜、断鼻型油藏分布区，还可能有混合型油藏；中部洼陷带为岩性油藏、裂隙型油藏发育区；斜坡带主要发育断鼻型油藏。     

准噶尔盆地西北缘侏罗系储层

准噶尔盆地西北缘侏罗系陆相碎屑岩储层的岩性差异较大，岩性对物性的控制作用明显。储层的孔隙类型多样，不同类型的孔隙在发育规模、丰度及有效性方面都存在显差异，次生溶蚀孔隙、原生粒间孔隙和残余粒间孔隙是最重要的有效孔隙类型。储层渗透率与孔隙度之间存在较好的半对数相关关系。通过设置一定的孔隙度和渗透率参数界线，对储层储集性能进行评价，将侏罗系储层的孔渗性能划分为5个级别，可与当前流行的砂岩储层孔渗性能分级相对应。通过对大量压汞参数样本的聚类分析，将储层的孔隙结构划分为4个类型。通过各类参数统计及曲线形态对比，对孔隙结构类型进行了定量结合定性的优劣评价。最后，结合孔渗性能级别、储集空间类型、孔隙结构类型、岩性等特征，对准噶尔盆地西北缘侏罗系储层进行了综合分类评价。     

平落坝储层有机包裹体特征与气藏形成过程研究

通过储集层成岩作用与有机包裹体的研究认为,研究区储集层有机包裹体主要通过交代和重结晶作用而形成,有各种相态形式,主要分布在石英颗粒内溶蚀缝或孔隙中,构造裂缝中基本未见有机包裹体。上三叠统储集层包裹体丰度明显高于侏罗系沙溪庙组。香二气藏砂岩有机包裹体均一温度主峰在 10 0～ 110℃;沙溪庙气藏砂岩有机包裹体均一温度主峰在 90～ 10 0℃。香二气藏形成时间早,经历了印支期少量注入到印支期末-喜山早期大量注入,再到喜山晚期调整、部分注入的过程。沙溪庙气藏天然气注入则主要发生于喜山运动期。     

库车坳陷侏罗纪沉积环境和层序地层分析

通过对库车坳陷野外露头和钻井资料以及地震剖面的综合分析,对库车盆地侏罗纪沉积环境、层序划分进行了研究.库车盆地在侏罗纪时期为一非对称型坳陷型盆地,主要物源在盆地的北部.划分了13个三级层序,三个层序组,反映了三个大级别的旋回.最大湖侵期为阳霞组中上部,与当时有一个明显的气候变热期相一致.沉积环境在侏罗纪早期为辫状河-辫状河三角洲环境、中期为曲流河-三角洲环境,后期为三角洲和浅湖环境,中期有短暂的海泛发生.影响侏罗纪湖平面变化的主控因素为构造运动、气候变化、物源条件、河水的流入以及海侵的影响.在中侏罗世早期、晚期的最大湖侵和海泛的短暂时期,形成了厚层的烃源岩分布.库车坳陷侏罗系虽然砂体分布广泛,厚度较大,然而由于陆相沉积环境的控制,非均质性较强、