Fast FILTERSIM Simulation with Score-based Distance

FILTERSIM is a pattern-based multiple-point geostatistical algorithm for modeling both continuous and categorical variables. It first groups all the patterns from a training image into a set of pattern classes using their filter scores. At each simulation location, FILTERSIM identifies the training pattern class closest to the local conditioning data event, then samples a training pattern from that prototype class and pastes it onto the simulation grid. In the original FILTERSIM algorithm, the selection of the closest pattern class is based on the pixel-wise distance between the prototype of each training pattern class and the local conditioning data event. Hence, FILTERSIM is computationally intensive for 3D simulations, especially with a large and pattern-rich training image. In this paper, a novel approach is proposed to accelerate the simulation process by replacing that pixel-wise distance calculation with a filter score comparison, which is the difference between the filter score of local conditioning data event and that of each pattern prototype. This score-based distance calculation significantly reduces the CPU consumption due to the tremendous data dimension reduction. The results show that this new score based-distance calculation can speed up FILTERSIM simulation by a factor up to 10 in 3D applications.     

Laboratory measurement of deformation-induced hydro-mechanical properties of reservoir rock in deep saline aquifers: An experimental study of Hawkesbury formation

The long-term integrity of CO₂ storage in deep saline aquifers has become uncertain due to the unsteady character of surrounding factors, and the time-dependent nature of the aquifer's overburden load (the vertical stress imposed on the aquifer by the weight of overlying materials (rock/soil layers), which may vary over time as a result of natural incidents such landslides and earthquakes) is critical. The aim of this study is to identify the influence of overburden load variations on the long-term integrity of the CO₂ storage process in deep saline aquifers. High-pressure tri-axial strength and permeability tests, along with acoustic emission (AE) and scanning electron microscopy (SEM) analyses, were conducted on Hawkesbury sandstone obtained from the Gosford basin.According to the results, the injection of CO₂ into the Hawkesbury formation may dissolve aquifer rock minerals, enhancing aquifer flow performance and reducing aquifer strength. Increasing the stress applied on the aquifer causes aquifer flow ability to reduce to some extent due to pore matrix compaction. Further increase of the overburden pressure may accelerate the aquifer's flow performance due to dilation-induced pore opening. This permeability transition point occurs earlier at greater CO₂ injection pressures and overlaps with the crack formation point of the aquifer rock mass. Therefore, weakening of the rock mass after the transition point can be expected. Importantly, this permeability transition point occurs at lower overburden loads after longer interaction of CO₂ with the saline aquifer. This exhibits the long-term risk associated with CO₂ sequestration in saline aquifers. Permeability enhancement after the transition point may also produce environmental disasters, such as sudden leakages of injected CO₂ from the reservoir to surrounding fresh water aquifers (Evans et al. 2004; Little and Robert 2010), exceeding the specific rates proposed by many regulatory frameworks. Therefore, it is essential to study the long-term integrity of the sequestration process in order to develop a regulatory structure to meet the demands of deep saline sequestration projects.     

A method for examining the geospatial distribution of CO2 storage resources applied to the Pre-Punta Gorda Composite and Dollar Bay reservoirs of the South Florida Basin,U.S.A.

This paper demonstrates geospatial modification of the USGS methodology for assessing geologic CO₂ storage resources, and was applied to the Pre-Punta Gorda Composite and Dollar Bay reservoirs of the South Florida Basin. The study provides detailed evaluation of porous intervals within these reservoirs and utilizes GIS to evaluate the potential spatial distribution of reservoir parameters and volume of CO₂ that can be stored. This study also shows that incorporating spatial variation of parameters using detailed and robust datasets may improve estimates of storage resources when compared to applying uniform values across the study area derived from small datasets, like many assessment methodologies. Geospatially derived estimates of storage resources presented here (Pre-Punta Gorda Composite = 105,570 MtCO₂; Dollar Bay = 24,760 MtCO₂) were greater than previous assessments, which was largely attributed to the fact that detailed evaluation of these reservoirs resulted in higher estimates of porosity and net-porous thickness, and areas of high porosity and thick net-porous intervals were incorporated into the model, likely increasing the calculated volume of storage space available for CO₂ sequestration. The geospatial method for evaluating CO₂ storage resources also provides the ability to identify areas that potentially contain higher volumes of storage resources, as well as areas that might be less favorable.     

Diagenesis and reservoir properties of Middle Jurassic sandstones,Traill Ø, East Greenland: The influence of magmatism and faulting

The c. 500 m thick Middle Jurassic sandstones of the fluvial Bristol Elv and marine Pelion Formations of the East Greenland Basin are evaluated here in order to improve the understanding of the processes that influenced the diagenetic evolution. The study may help to predict the reservoir properties of sandstones affected by magmatism and faulting, both in general and specifically in undrilled areas on- and offshore East Greenland and, in the Vøring Basin on the Mid-Norwegian shelf. The study shows a variety of authigenic mineral phases dominated by quartz cement, carbonate cement, illite and iron-oxide. One of the clear differences between the two formations is the presence of early carbonate-cemented horizons in the marine sandstones; these horizons are inferred to reflect a primary concentration of biogenic clasts and fossil shells. Intense quartz cementation occurs primarily in the fluvial sandstones but the marine sandstones are also highly quartz-cemented. Two episodes of burial and uplift are recorded in the diagenetic sequence and widespread grain-crushing in coarse-grained intervals is believed to result from overpressure and subsequent compaction due to sudden pressure release along major faults. Maximum burial depths may only have been around 2000–2500 m. Cathodoluminescence analyses show that grain crushing was followed by intense quartz cementation. The quartz cement is to a great deal believed to have formed due to increased surface area from crushing of detrital quartz grains, creating fresh nucleation sites for the quartz. Cathodoluminescence investigations also show that only minor pressure dissolution has taken place between detrital quartz grains and that the ubiquitous quartz cementation displays several growth zones, and was thus in part the result of the introduction of silica-rich extra-formational fluids related to the flow of hot fluids along reactivated faults and increased heat flow and temperature due to magmatism. This interpretation is supported by fluid inclusion homogenization temperatures between 117 and 158 °C in quartz cements. In one of the two study areas, the development of macroscopic stylolites has significantly enhanced quartz cementation, probably in connection with thermal convection flow. As a result of the magmatic and fault-related quartz cementation and illitization, the reservoir quality of the sandstone formations deteriorated and changed drastically.     

Baselines of acceptability and generational change on the Mactaquac hydroelectric dam headpond (New Brunswick,Canada)

Hydroelectricity is an old yet reliable form of renewable energy, with acknowledged social and ecological impacts. A tension currently exists between such concerns and energy needs, with dam construction and removal ongoing around the world. It is critical to better understand the implications of both on local citizens. We performed map elicitation interviews with 20 locals around the prematurely-aging Mactaquac Dam and headpond, in New Brunswick, Canada, to understand if and how they came to accept the dam landscape, and what they want for its future. A Baselines of Acceptability conceptual framework was developed to guide the interpretation. Respondents demonstrated attachment to the dam-in-place landscape, even those initially disadvantaged by its construction, and a preference for keeping the headpond intact. Despite this demonstrated adaptability, the paper calls for improved transparency, scope and justice in energy landscape decision-making, as well as further testing of the framework with different demographics, infrastructure case studies and over time.     

基于动库容曲线的水库调洪高水位查算方法研究

河道型水库因动库容特性显著,传统的静库容调洪方法难以适用,研究动库容调洪方法是亟待解决的问题。当坝前水位爬升到最高点时,库区内的洪水演进到达一种临界状态,库区内的水文、水力条件相对稳定,在出库流量和入库流量一定的情况下,可望获得最高坝前水位与同时刻库容之间良好的对应关系。依托三峡库区水文水动力耦合预报模型,建立了一组以出库流量、入库流量为参数的动库容曲线,以供调洪时快速查算最高坝前水位。采用2009年以来三峡水库16场场次洪水资料,检验所建动库容曲线的合理性。结果表明,各场洪水的最高库水位查算值与实况平均偏差仅0.20m,证明建立的基于动库容曲线的三峡水库最高库水位查算方法具有较好的实践价值。     

涪陵气田焦石坝区块页岩气储层储集空间特征及其定量评价

四川盆地涪陵气田焦石坝区块上奥陶统五峰组—下志留统龙马溪组一段海相页岩气储层是由孔隙和裂隙组成的双孔隙岩层。为确定储层的含气量和产出能力,应用页岩气测井评价技术对储层的孔隙度和渗透率进行了定性认识,并提出了定量评价方法。认为用"经验统计法"可以有效计算出页岩气储层的孔隙度,但由目前的测井评价技术所得到的渗透率仅能反映储层渗透率的变化趋势。     

四川盆地中部龙王庙组滩相储层特征及形成机制

依据岩心、常规薄片及铸体薄片、物性分析、压汞等资料的研究,四川盆地中部下寒武统龙王庙组滩相储层为发育良好的中低孔、低渗的孔隙型储层及裂缝—孔隙型储层。储集岩主要为砂屑白云岩、鲕粒白云岩与具残余颗粒结构的粉—细晶白云岩,储集空间主要包括粒间溶孔、粒内溶孔、晶间溶孔、铸模孔、残余粒间孔、裂缝及溶洞,孔喉配置关系好。储层形成机制研究表明,滩核和滩翼微相有利于储层发育,滩相储层在沉积早期具有典型的宏观非均质性,这为储层的形成与演化提供了物质基础。同生岩溶作用控制了早期储层的孔隙演化,表生岩溶作用决定了储层分布的基本特征,埋藏岩溶作用有利于先期孔渗层的优化改造。提出滩相储层的演化主要经历三个阶段,其中沉积—同生成岩阶段是早期优质储层形成的关键时期,表生岩溶改造阶段是滩相储层大规模增孔时期,埋藏成岩阶段为滩相储层孔隙调整和稳定时期。     

渤海典型低孔低渗油藏储层预测及效果——以渤海A油田沙河街组二段为例

综合利用地震、钻井、测井等资料,从渤海A油田古近系沙河街组二段的地层发育特征入手,以砂体发育特征与地震资料响应的匹配关系为研究思路,探究古地貌分析、地震属性分析等手段对研究区沙二段储层预测的适用性。通过开展最大振幅之和的地震属性计算、已钻井砂体厚度趋势约束、古地貌联合校正的储层预测,表明在沙二段沉积时期研究区主要为沟谷与洼地被两凸起分隔的古地貌格局,有利储层主要发育在西南及东北古地貌低洼处,东北部是后期开发调整的潜力区。基于该储层预测方法的合理性得到了5口设计井实钻结果的检验,证实了该成果不仅有助于油田下步调整方案的制定和实施,而且储层预测的思路和方法也可供海上类似中深层油田借鉴。