【作者】 杨大刚；

【导师】 贾振岐；

【作者基本信息】 大庆石油学院 ， 油气田开发工程， 2008， 博士

【摘要】 低渗透油田注水开发是一个世界级的难题。低渗透储层本身的潜在损害因素被外来流体诱导,容易发生多种储层损害,造成堵塞,从而降低流体在地层中的渗流能力,引起注水井注入压力升高,注入能力下降,进而使油井产能下降,油水井间难以建立起有效的驱动体系。大庆油田萨中开发区萨零组油层属三角洲外前缘沉积砂体,是典型的低渗透砂岩储层,具有一定的油气丰度和地质储量,但储层粘土含量高,具有强水敏、偏强速敏性质,开发难度大。本研究在了解、掌握国内外低渗透油田注水开发防膨、解堵状况的基础上,深刻剖析萨零组油层的地质特征,从以下几个方面开展了大量研究,探索了萨零组油层注水开发的可行性。针对试验区解释厚度小而产油能力相对较高、原被扣除的高阻夹层中部分层具有含油产状的情况,在研究细化含钙储层类型和四性关系的基础上,重新选择对含钙储层岩性响应好的电测曲线,制定了含钙储层电性研判标准,采用微电极幅度差比值、尖锐度,声波回返程度、方波、密度曲线共5种参数综合判别含钙储层,制定了含油钙电性判定新标准和含油钙储层细化新标准。新标准进一步细化了含油层系,重新核实了地质储量,与试验区动态资料吻合较好。结果表明,试验区判钙划准率从79.6%上升到92.8%,提高了13.2%。进一步补充和完善了萨零组储层划分操作规程。使用X射线衍射仪、扫描电镜、原子吸收光谱等手段,检测了萨零组储层性质。萨零组油层属中低孔隙度、低渗透储层,粘土矿物含量高,主要为蒙脱石、伊利石和高岭石,其中以高岭石为主;油层岩心表面颗粒排列较紧密;孔隙发育较差,连通性较差;颗粒表面生长有次生石英;长石颗粒易被溶蚀。根据砂岩储层敏感性评价实验程序行业标准,对萨零组岩心进行的“五敏”室内实验评价后认为:萨零组储层为强水敏、偏强速敏、强盐敏、中等偏强酸敏、弱压敏储层。在注水开发过程中主要解决好强水敏和偏强速敏对油层造成的损害。对不同类型粘土稳定剂利用凯式定氮法测定有效物含量,用离心法测定防膨率,用静态失重法测定溶失率,用X射线衍射法测定钙蒙脱石在浸泡粘土稳定剂、饱和乙二醇蒸汽和水洗实验前后的晶面间距,用岩心流动实验进一步评价防膨效果、优化防膨剂最佳注入量和注入周期,用静态吸附法测定吸附滞留量,通过比较分析实验结果后认为:氯化钾型粘土稳定剂DNT-14具有良好的性能指标,其最佳浓度为3.0%,与地层水及优选解堵配方体系溶液都具有良好的配伍性,最大程度降低了粘土稳定剂本身造成的粘土膨胀,不易被水分子或有机分子取代,耐冲洗能力强,静吸附量最低,最佳的注入量为5PV～10PV,最佳注入周期为5PV～10PV。通过对萨零组储层岩心溶蚀率、破碎率实验评价及长、短岩心解堵模拟实验研究,优选出萨零组储层的解堵配方: 12%HCl+0.5%HF+0.5%HBF4+3%CH3COOH。该解堵液体系的主要特点为:①能较好地增加岩心的渗透率、保持岩心的强度和完整性;②缓速性能好,能有效降低酸岩反应速度,增大酸的作用距离,达到深度酸化作用;③酸液体系中的粘土稳定剂、缓蚀剂、铁离子稳定剂效果良好,防酸渣性能优良。酸液体系各组分和配比合理,能有效减少酸化过程中的二次伤害,满足现场施工条件。针对试验区先期生产井供液能力均较差、不能连续生产的问题,在试验区1口井限流法压裂取得较好效果并对压后油层产能和流体物性进行评估的基础上,结合萨零组储层特征,从压裂液体系、支撑剂体系以及压裂工艺三方面进行试验研究,解决了萨零组压裂改造过程中的储层敏感性和支撑剂镶嵌问题,创生出防膨压裂工艺。利用室内研究结果,开展了萨零组储层添加不同浓度粘土稳定剂条件下的矿场水驱试验研究,验证并确定了注入水中最佳的粘土稳定剂浓度。该研究形成了萨零组储层精细地质研究、防膨压裂、复配酸解堵及注水开发配套技术,创新出萨零组“五敏”特性下的注水开发工艺。实践证明,萨零组油层注水开发可行,水驱采收率在15%左右。该技术推广潜力较大,在大庆喇萨杏油田具有广阔的应用前景。更多还原

【Abstract】 Water injection at Low permeability oilfield has become a piece of world-class puzzle. The local potential damage factors at Low permeability reservoir are provoked by foreign fluids to cause multiple formation damage and bring about plugging,which then reduces the percolation of fluids at reservoirs, enhance the injection pressure of injection wells, decrease the injection capacity, and further reduce the oil well productivity, so it is difficult to build a effective driving system between oil and water wells. The Saertu oil layers at Daqing oilfield belong to a kind of sedimentary exterior sandstone body at delta region. It is a typical low permeability sandstone reservoir, which have definite oil and gas richness and geological reserves. Yet it is difficult to develop this reservoir because of high clay content that causes strong water-sensitivity and velocity sensitivity. On the bases of a lot of data about swelling proof and unplugging for home and abroad low permeability oilfield developmnent by waterflooding, the geologic characteristics of the Saling Group oil layers are overall understood. Then a great many of studies are performed from several aspects as follows to know the feasibility of waterflooding type at oil layers of Saling Group.Aiming at such cases of small interpreted thickness but high productive capacity and of oil-bearing occurrence at some layers of high-resistance interlayer deduced originally, on the bases of refinement of calcium reservoir types and four propertied, electric logs in response well to calcium reservoir lithology are renewed to establish a determination standard of calcium electrical reservoir electrical property. New standards for judging electrical properties within oil-bearing calcium and refining oil-bearing reservoir are established with 5 parameters to identify calcium reservoir such as Microelectrode Amplitude Difference Ratio, Sharpness, and Sound Wave Reversion Degree, Square Wave and Density curves together. The new Standards further refine the oil-bearing series, verify the geological reserves again that is consistent with the pilot performance data well. The precision of calcium judgment at the testing area has been enhanced by 13.2% from 79.6% up to 92.8%. This work further supplement and perfect the operation specifications of reservoir division at Saling Group.The reservoir properties of Saling Group are checked by several instruments as X-ray diffractometer, scanning electron microscope and atomic absorption spectrum, etc.. The Saling Group is a mediately and low porous, low permeable reservoir with high content of clay minerals include smectite, illite and kaolinite,among which the kaolinite has the most content. The grains at core surface arrange relatively compactly at the reservoir. The porosity develops poorly with bad connectivity. Secondary quartz grows on the particle surface. The feldspar particles can easily be eroded. 5 sensitivities of Saling Group cores are evaluated in lab according to the Experimental Sequence Industry Standard of Sandstone Reservoir Sensibility Evaluation. The Saling Group is a kind of strong water-sensitivity, partly strong velocity-sensitivity, strong salt-sensitivity, Moderate apt to strong acid-sensitivity, inferior pressure-sensitivity. In the process of waterflooding, the damage caused by strong water-sensitivity and partly strong velocity-sensitivity should be good dealt with.The valid content, swelling proof ratio and dissolution ratio of different types of clay stabilizer are measured by methods of Kjeldahl Nitrogen determination, centrifuging and static weight loss aspectly. The interplanar distances of Ca-smectite before and after soak by clay stabilizers, saturation by glycol vapor and water cleaning are measured by X-ray diffraction method in lab. The antiswelling effect is evaluated further by core flow experiments to optimize the optimal injection rate and period of the antiswelling agent. And the adsorptive retention is measured by static adsorptive process. The conclusions gained from the comparative analysis with the experimental results are as follows: DNT-14 is a type of clay stabilizer of potassium chloride with favorable performance index; its optimum concentration is 3.0%; it is well compatible with formation water and/or the optimized unplugging formulation system; it reduces the degree of the clay swelling by itself to the maximum; it is difficult to be replaced by water molecules or organic molecules; it has strong capacity against water washing; it has less static adsorption; its optimum intake volume and injection period are the same as 5～10PV.The unplugging formulation for the Saling Group is optimized by evaluation of erosion ratio and breaking ration of cores and from modeling experiments with long and short cores in lab, which is 12%HCl+0.5%HF +0.5%HBF4+3%CH3COOH. The principal features of the unplugging fluid system are as follows:①it could preferably increase cores’ permeability and keep the cores’ intensity and integrality;②its good performance of reaction velocity reduction could effectively decrease the reaction rate of acid-rock to increase the acerbic range to achieve deep acidification;③The clay stabilizer, corrosion inhibitor Fe-stabilizer in the acid system have good effect for acid residue prevention, and every component and the mixture ratio in the acid system are reasonable which could effectively reduce the secondary damage in the process of acidization and fit for the site operation.Aiming at the early production wells at the testing area that could not produce continuously for bad flowing capacity, on the bases of a successful flow limited fracturing and post evaluation of reservoir productivity and fluid properties for a well, in combination with the reservoir properties, the questions about reservoir sensitivities and propping agent incrustation are solved in the process of fracturing from 3 aspects as fracturing fluid system, propping agent system and fracturing technology. A new fracturing technology is put forward.Based on the results in lab, waterflooding field test was carried out under conditions of diffirent clay stabilizer concentration at the Saling Group reservoir. And the optimum concentration of the clay stabilizer in injection water was decided.In these studies, a series of technologies such as the fine geologic research, antiswelling fracture, unplugging with composite acids and correlated waterflooding methods have become a new system for the development by waterflooding at the Saling Group with "5 sensitivities”. The practice proves that it is feasible for the Saling Group to be developed by waterflooding with water recovery of about 15%. This technological system has good potential and prospect for application at the La-Sa-Xing oilfield in Daqing.更多还原