EFFECT OF MICRITE CONTENT ON CALCITE CEMENTATION IN AN UPPER JURASSIC CARBONATE RESERVOIR,EASTERN SAUDI ARABIA

Cementation is a primary factor reducing the porosity of carbonate rocks. It is a challenge to accurately model cementation for reservoir quality prediction because cementation is often a syndepositional process. In addition, cementation requires fluid flow to transport chemical species for precipitation within the pore spaces in a sediment. The development of fully‐coupled depositional‐hydrogeochemical models for cementation prediction is desirable, but the parameters which control the extent of cementation need to be identified and evaluated. This study uses petrographic data from 583 carbonate samples from 15 wells in an Upper Jurassic (Kimmeridgian) reservoir at a giant oilfield in eastern Saudi Arabia to investigate the controlling effects of micrite content on cementation in carbonate rocks. The results indicate that the amount of cement decreases with increasing micrite content in the carbonate rocks analysed. In addition, a modified Houseknecht method has been developed to assess the relative fractions of porosity reduction in carbonate sediments due to compaction and cementation. The method highlights variations in depositional porosity for different rock textures and distinguishes microporosity from interparticle porosity. In the studied samples, the total porosity loss due to compaction and cementation is generally less than 45%, and samples lose more porosity due to compaction than cementation. The relative importance of compaction and cementation in reducing porosity is different for different rock textures: wackestones and mudstones lose porosity mostly as a result of compaction, while grainstones, mud‐lean packstones and packstones lose porosity due to both compaction and cementation.     

Influence of soil density on gas permeability and water retention in soils amended with in-house produced biochar

Biochar has been used as an environment-friendly enhancer to improve the hydraulic properties(e.g.suction and water retention) of soil.However,variations in densities alter the properties of the soil-biochar mix.Such density variations are observed in agriculture(loosely compacted) and engineering(densely compacted) applications.The influence of biochar amendment on gas permeability of soil has been barely investigated,especially for soil with diffe rent densities.The maj or obj ective of this study is to investigate the water retention capacity,and gas permeability of biochar-amended soil(BAS) with different biochar contents under varying degree of compaction(DOC) conditions.In-house produced novel biochar was mixed with the soil at different amendment rates(i.e.biochar contents of 0%,5% and 10%).All BAS samples were compacted at three DOCs(65%,80% and 95%) in polyvinyl chloride(PVC)tubes.Each soil column was subjected to drying-wetting cycles,during which soil suction,water content,and gas permeability were measured.A simplified theoretical framework for estimating the void ratio of BAS was proposed.The experimental results reveal that the addition of biochar significantly decreased gas permeability k_g as compared with that of bare soil(BS).However,the addition of 5%biochar is found to be optimum in decreasing kg with an increase of DOC(i.e.k_(g,65%) k_(g,80%) k_(g,95%)) at a relatively low suction range(200 kPa) because both biochar and compaction treatment reduce the connected pores.     

惠民凹陷临南洼陷古近系沙河街组超压成因机制及分布预测

渤海湾盆地惠民凹陷临南洼陷古近系沙河街组油气勘探过程中钻遇不同规模的异常高压，超压成因的不确定性限制了压力预测的可靠性。利用临南洼陷丰富的钻杆测试（DST）压力数据、泥浆密度和测井资料，细致分析了渗透性砂岩流体压力发育特征和超压段泥岩测井响应，依据常压和超压段声波速度、密度测井数据建立判识超压成因的有效应力-测井响应图版，综合讨论了沙河街组超压的成因机制，并预测了异常高压的空间分布。研究发现，临南洼陷沙河街组砂岩储层超压主要发育在3 000 m以深的沙三段（Es³）和沙四段（Es⁴），最高过剩压力分别为23.82 MPa和14.04 MPa；超压段泥岩测井响应表现为偏离正常压实趋势的异常高声波时差、低密度和高中子孔隙度，具有典型的欠压实特征。沙河街组储层超压最主要的成因是相邻泥岩机械压实不平衡作用形成超压的传递，表现为大多数的超压数据均符合加载曲线趋势，只有深洼陷区（埋深为4 000~4 300 m）的超压呈现出卸载特征，可能存在由于富有机质泥岩深埋达到较高成熟度（R_o为0.90%~1.05%）引起的生烃增压贡献。利用平衡深度法计算的流体压力与DST压力数据吻合度高，印证了沙河街组超压主要来自泥岩不均衡压实作用的认识，沙三段过剩压力呈现围绕着洼陷中心呈环状分布，向周围的斜坡区和隆起带逐渐减小为常压。研究成果可以为临南洼陷钻前压力评估提供有价值的指导和借鉴。     

综采工作面覆岩压实区演化采高效应分析及应用

采用相似材料物理模拟试验及理论分析，研究在不同采高条件下覆岩压实区的动态演化规律及形态特征。研究结果表明:在煤层开采之后，采动覆岩离层量分布呈“马鞍”状，采空区底板在一定区域内存在应力集中，结合两者可作为压实区底部边界判定依据;采空区覆岩压实区的形态及时空演化规律受采高与工作面推进距离的共同影响，得到了压实区宽度、高度及垮落角度的演化规律与采高的关系;同时，结合冒落带岩体的碎胀特征与底板应力集中的特点，分析了压实区压实程度的采高效应，即在一定范围内，采高越高，压实程度越大。基于采动裂隙椭抛带理论，在试验结果分析的基础上，建立了采动裂隙椭抛带压实区的数学表达方程，为卸压瓦斯抽采系统的布置及参数优化提供借鉴。     

渤海湾盆地南堡凹陷异常压力系统及其形成机理

渤海湾盆地南堡凹陷异常压力现象普遍发育，但对于凹陷中不同构造带异常压力的刻画与成因机制的探讨却较为薄弱。利用357口井1 354个钻杆测试数据（DST）和重复地层压力测试数据（RFT），测井曲线资料等，详细刻画了不同构造带的压力结构特征。研究表明：南堡凹陷地层压力系统纵向上可划分为3个带，浅部常压带（<1 800 m）、中部过渡带（1 800~2 400 m）和深部异常高压带（>2 400 m）。沙三段发育大规模异常高压，压力系数最高达1.9，超压带顶界面深度约为2 400 m；老爷庙构造带中、浅层发育低幅度超压带，压力系数约为1.2；滩海地区东一段和东二段局部发育异常低压。利用数值模拟技术和垂直有效应力-声波时差判别图版等方法，并结合烃源岩生排烃过程综合分析等，深入探讨了南堡凹陷不同异常压力系统的形成机理，研究认为：①深部沙三段的大规模超压主要来源于东营时期的泥岩不均衡压实作用，生烃作用也有一定贡献，但相对前者贡献较小；②明化镇时期，生烃作用是最主要的增压机制，而欠压实作用贡献则相对有限；③中浅层低幅超压带来源于深部超压的“传导”，开启的断裂带为其传递通道；④东营末期的区域抬升剥蚀作用引起岩石骨架孔隙回弹和流体收缩，是形成本区异常低压的主要原因。     

Computational intelligence modelling of pharmaceutical tabletting processes using bio-inspired optimization algorithms

In pharmaceutical development, it is very useful to exploit the knowledge of the causal relationship between product quality and critical material attributes (CMA) in developing new formulations and products, and optimizing manufacturing processes. With the big data captured in the pharmaceutical industry, computational intelligence (CI) models could potentially be used to identify critical quality attributes (CQA), CMA and critical process parameters (CPP). The objective of this study was to develop computational intelligence models for pharmaceutical tabletting processes, for which bio-inspired feature selection algorithms were developed and implemented for optimisation while artificial neural network (ANN) was employed to predict the tablet characteristics such as porosity and tensile strength. Various pharmaceutical excipients (MCC PH 101, MCC PH 102, MCC DG, Mannitol Pearlitol 200SD, Lactose, and binary mixtures) were considered. Granules were also produced with dry granulation using roll compaction. The feed powders and granules were then compressed at various compression pressures to produce tablets with different porosities, and the corresponding tensile strengths were measured. For the CI modelling, the efficiency of seven bio-inspired optimization algorithms were explored: grey wolf optimization (GWO), bat optimization (BAT), cuckoo search (CS), flower pollination algorithm (FPA), genetic algorithm (GA), particle swarm optimization (PSO), and social spider optimization (SSO). Two-thirds of the experimental dataset was randomly chosen as the training set, and the remaining was used to validate the model prediction. The model efficiency was evaluated in terms of the average reduction (representing the fraction of selected input variables) and the mean square error (MSE). It was found that the CI models can well predict the tablet characteristics (i.e. porosity and tensile strength). It was also shown that the GWO algorithm was the most accurate in predicting porosity. While the most accurate prediction for the tensile strength was achieved using the SSO algorithm. In terms of the average reduction, the GA algorithm resulted in the highest reduction of inputs (i.e. 60%) for predicting both the porosity and the tensile strength.     

粉土地基强夯加固效果影响因素数值模拟研究

以绍兴新东线软基加固工程为背景，采用ABAQUS对强夯加固粉土地基进行模拟，结合现场实测数据分析了夯击次数、夯击能、落距和水位对强夯加固效果的影响。结果表明:锤侧土体塑性应变等值线近似于半椭圆形，随夯击次数的增加，塑性区逐渐增大，且其增量以夯锤侧下方为主；不同夯击能下，强夯的有效加固深度与累积夯沉量比值介于4~5；“轻锤高落”产生的锤土接触应力峰值较“重锤低落”大，但衰减速度更快；地下水位越高，浅部土体强夯产生的超静孔隙水压力及其增幅越大；降低水位可显著提升强夯加固深度。