沁水盆地寿阳勘探区煤层气井排采水源层判识

煤层气井水源层判识,对于单井排采动态诊断、优选作业井层和制定科学的压裂方案均具有重要意义。针对寿阳勘探区煤层气井高产水问题,开展了区域水动力场和能量场、煤系砂岩和灰岩含水性、目标煤层围岩岩性连井对比、井筒与煤层围岩含水层连通关系以及典型煤层气井水源层剖析等方面的研究。研究表明,区域水动力场和煤层渗透率是煤层气井平均产水水平的决定因素,而煤层气井产水量的井间差异主要受控于单井波及范围内局部地质工程因素(断裂、压裂缝类型和高度及岩性组合),水力压裂缝是除断裂外煤层与围岩含水层沟通的一种方式。通过综合分析,本文取得的结论是,煤系砂岩是寿阳勘探区煤层气井的主要水源层,太原组灰岩对排采的影响有限。建议在煤层气开发井层优选和压裂方案设计时,重点考虑目标煤层与砂岩含水层的垂向组合关系。     

基于含水层-钻孔水量交换的疏水钻孔水量计算

疏水降压是煤矿顶板水害防治的主要工程手段,复合充水含水层中倾斜疏放水钻孔涌水量计算及参数优化是需要解决的关键技术。以“渗流-管流耦合模型”理论及能量守恒定律为基础,以含水层-钻孔间水量交换量为耦合点,构建了煤层顶板复合充水含水层倾斜疏放水钻孔定降深放水的含水层-钻孔系统耦合模型,利用母杜柴登矿井临时煤仓放水试验数据验证了模型的可靠性。以此为基础,计算了不同钻孔仰角、数量的钻孔涌水量及单位长度涌水量,确定了钻孔的最佳仰角和数量。同时,计算分析了150 m钻场间距下600 m工作面范围内不同疏降水头的钻孔涌水量、工作面内部降深的特征。结果表明:基于含水层-钻孔水量交换的疏放水钻孔水量计算模型充分考虑了疏放水过程中钻孔内的层流和紊流水流特征。模型计算的1个主放水孔水量和2个观测孔水位历时变化和现场实际情况基本一致,模型可靠性好,且能解决倾斜钻孔在复合充水含水层中的水量分配问题。随着疏放水钻孔仰角的增大,单位长度的钻孔涌水量呈现先增加后减小的趋势,在仰角为60°时,钻孔单位涌水量最大,稳定水量为165 m3/h,主要涌水层位为直罗组一段含水层,约占总涌水量的81%。此外,随着钻孔数量增加,单个钻场内钻孔总涌水量不断增加,单位长度的钻孔涌水量呈现逐步减小的趋势,钻孔数量增至5个后总涌水量基本稳定,钻孔稳定总涌水量约为440 m3/h。在150 m钻场间距下600 m工作面范围中,60 d内,780 m定水头疏降时,钻孔总涌水量由1 700 m3/h降至170 m3/h,降幅达90%;830和880 m定水头疏降下,钻孔总涌水量由1 530,1 350 m3/h分别降至153,135 m3/h,降幅均为90%。钻场内钻孔总涌水量受到周边钻场疏降干扰的影响,由两端向内侧影响逐步增大。780 m定水头疏降时,两端钻孔总涌水量约为309 m3/h,最中间钻场钻孔总涌水量约为142 m3/h。工作面内部水头分别降至780,830和880 m的时间分别为155,125和100 d。随着时间推移,不同降深范围逐步增大。随着疏放时间的延续,横剖面呈现以倾斜钻孔为中心的降落漏斗且范围逐步扩大,平面上则呈现以全部钻场范围为中心的降落漏斗且范围逐渐增大。     

Investigation of the pH effect of a typical host rock and buffer solution on CO2 sequestration in synthetic brines

Carbon dioxide sequestration in deep saline aquifers is a critical component of long-term storage options. It is suggested that the precipitation of mineral carbonates is mostly dependent on brine pH and is favoured above a basic pH of 9.0. However, brine pH will drop to acidic values once CO₂ is injected into the brine. Therefore, there is a need to raise brine pH and maintain it stable. Synthetic brines were used here instead of natural brines because of the difficulty in obtaining and storing natural brines. Therefore, experiments were conducted to prepare a series of synthetic brines and to compare their suitability to natural brines for carbon sequestration firstly. A typical host rock (Oriskany rock) and a buffer solution (NaCl/NaHCO₃) were selected to buffer brine pH. In a subsequent step, studies were conducted to correlate how brine samples respond in the presence of the host rock or the buffer solution at realistic reservoir temperatures (40 and 100 °C) and pressures (1160 and 1500 psi) for CO₂ storage. The results show that synthetic brines prepared can be used as analogues as natural brines for carbon sequestration studies in terms of chemical composition and pH response. Both XRD and SEM/EDS analyses confirmed the presence of mineral carbonates in the CO₂-rock-brine and the CO₂-buffer-brine experiments. However, the amount of carbonates precipitated from the CO₂-buffer-brine reactions is nearly 18 times larger than that formed from the CO₂-rock-brine experiments. ICP-MS studies also verified that there was only 4% reduction in Ca concentration in solution after the CO₂-rock-brine studies, while the concentrations of Ca and Sr decreased by 90% during the CO₂-buffer-brine experiments.     

Strategy for solving semi-analytically three-dimensional transient flow in a coupled <Emphasis Type="Italic">N</Emphasis>-layer aquifer system

Efficient strategies for solving semi-analytically the transient groundwater head in a coupled N-layer aquifer system , i = 1, ... , N, with radial symmetry, with full z-dependency, and partially penetrating wells are presented. Aquitards are treated as aquifers with their own horizontal and vertical permeabilities. Since the vertical direction is fully taken into account, there is no need to pose the Dupuit assumption, i.e., that the flow is mainly horizontal. To solve this problem, integral transforms will be employed: the Laplace transform for the t-variable (with transform parameter p), the Hankel transform for the r-variable (with transform parameter α) and a particular form of a generalized Fourier transform for the vertical direction z with an infinite set of eigenvalues (with the discrete index m). It is possible to solve this problem in the form of a semi-analytical solution in the sense that an analytical expression in terms of the variables r and z, transform parameter p, and eigenvalues of the generalized Fourier transform can be given or in terms of the variables z and t, transform parameter α, and eigenvalues . The calculation of the eigenvalues and the inversion of these transformed solutions can only be done numerically. In this context the application of the generalized Fourier transform is novel. By means of this generalized Fourier transform, transient problems with horizontal symmetries other than radial can be treated as well. The notion of analytical solution versus numerical solution is discussed and a classification of analytical solutions is proposed in seven classes. The expressions found in this paper belong to Class 6, meaning that the transformed solutions are written in terms of eigenvalues which depend on one transform parameter (here p or α). Earlier solutions to the transient problem belong to Class 7, where the eigenvalues depend on two transform parameters. The theory is applied to three examples.     

立井普通凿井法施工过含水土层

立井普通法施工条件是表土稳定,含非饱和水的粘土层,含少量水的砂质土层等。原设计不含水或含水量很少的土层,采用普通法施工的立井,在施工中,地质条件发生变化,遇见含水砂土,淤泥层、含饱和水的粘土层,就需要技术人员,根据现场的变化情况,采取应急的措施和方法,去解决和处理施工中发生的意外情况。     

Characterization and modelling of oil reservoirs and groundwater aquifers: application of Wavelet Transformations

We describe wavelet transformations (WTs) and their basic properties, and discuss their application to analysis of complex and noisy data. These transformations are a powerful tool for data and image analysis by (1) providing a flexible spatial- and/or time-scale window which narrows when one focusses on small-scale features and widens when one wishes to analyze large scale features, and (2) providing the capability for analyzing special characteristics of a set of data or images around specific points. We discuss application of WTs to developing a unified and highly efficient method for characterization and simulation of porous media problems, from pore to field scale. The method uses WTs for data mining and characterization, scale-up of the geological (fine-scale) model of porous media, and interpretation of their transient flow properties. The data that can be treated by WTs include the direct data, such as various well logs and the permeability distributions, and the indirect data, such as seismic signals, and other characteristics of porous media. Wavelet transformations denoise the data, uncover their special features, and discover the structure of their distribution. They also provide an efficient method for processing seismic data, which are typically in huge volumes. Wavelet transformations can also analyze time-dependent flow data, such as long-term production data for oil reservoirs, as well as time-dependent seismic data (i.e., repeated measurements over regular time intervals). Therefore, one has, for the first time, a unified approach to characterization and modelling of large-scale porous media and extraction of information from their flow properties, from pore to field scale. The computational cost of the method can be orders of magnitude less than those of the most efficient methods currently available. Received: 30 March 2000