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裂缝性低渗透油藏深度调剖技术研究


裂缝性低渗透油藏深度调剖技术研究/ 本文来自: 聚合吧(http://www.juhe8.com/) 详细出处参考: http://www.juhe8.com/lunwen/qita/2008-01-14/86958.html 朝阳沟油田属于裂缝性低渗透油藏, 处于油田主体部位的一类区块裂缝分布密度 0.13 条/m, 经过 17 年的注水开发,目前采出程度达到 20%,综合含水

48.7%。由于裂缝造成的注入水 指进和油藏非均质性影响,层间平面矛盾逐渐加剧,含水不断上升,且线性注水后注采系统 调整余地减少, 依靠常规技术手段进行调整挖潜的余地越来越小, 面临进一步改善区块开发 效果、提高采收率的实际要求,于是近两年开展了深度调剖技术研究,深度调剖可以有效地 封堵裂缝和高渗透带,使后续水进入基质扩大波及体积,缓解层间和平面矛盾,改善区块开 发效果。 根据油藏条件,主要考虑低渗透储层孔隙结构及裂缝特征,进行了调剖剂的配方 优选、性能评价、岩心封堵及封堵后驱油实验、核磁共振成像研究和凝胶对裂缝封堵环境扫 描电镜微观实验研究,优选出了与朝阳沟油田储层配伍的调剖剂配方。调剖剂由主剂、交联 剂和添加剂组成。主剂为 HPAM,交联剂主要原料为氯化铬,添加剂以硫脲为主。 深度调 剖选用的聚合物为部分水解聚丙烯酰胺,分子量为 1400 万,水解度 25%。室内模拟实验表 明,随着聚合物浓度的增加,溶液初始粘度和成胶粘度增高。综合考虑成胶粘度和实际注入 能力,确定适宜的聚合物浓度为 800-1200mg/l。通过实验有机铬体系不同交联比对成胶性能 的影响得出:随着交联比的增加,凝胶粘度增高。综合考虑成胶粘度及经济效益,确定合适 的交联比为 15: 实验表明 NaCI 和 NaHCO3 可以调整交联体系的交联速度, 1。 其浓度越大, 交联反应越快。 经筛选实验中加入 600-800mg/l 浓度的 NaCI 和 500-750mg/l 浓度的 NaHCO3 最适宜。使用硫脲作为配方中凝胶的稳定剂,其最佳浓度为 1000mg/l。室内实验表明,配 制的调剖剂在成胶前经地层水稀释形成的交联体系与地层水和注入水都具有良好的配伍性、 稳定性和较好的流度控制能力。含裂缝天然岩心驱油实验结果表明,水驱至残余油状态,岩 心用凝胶封堵,后续水驱岩心的采收率可提高 6.3 到 9.1 个百分点。核磁共振实验和微观仿 真模型实验结果表明:聚合物与交联剂混合溶液进入模型后沿裂缝运移,对裂缝进行充填, 成胶后对裂缝产生封堵作用,迫使后续注入水改变液流方向,进入模型基质部分,随后续水 驱的进行,波及体积逐渐扩大,使基质中封堵前不动的原油产生运移,模型出口有原油被驱 出,提高原油采收率。凝胶对含裂缝岩心封堵环境扫描电镜结果显示:凝胶对裂缝性油藏中 的裂缝具有较好的封堵效果,同时进入岩心基质的凝胶较少,保证其不会被凝胶封堵,后续 水可以从基质流过,提高基质的采收率。根据朝阳沟油田地质和流体特征,建立了平面地质 模型。模拟计算结果表明,高渗透条带的封堵半径在 1/5~1/3 井距的情况下,效果较好。 注入凝胶段塞尺寸为 0.02PV~0.04PV 的方案最佳。不同含水的注入时机对驱油效果的影响 较大,当含水为 70%-80%时,进行封堵,效果最好。在相同的凝胶段塞注入量下,为了避 免调剖液被稀释采取不同段塞注入的方式, 即先注一定量的前置液, 然后浓度由低到高依次 注入调剖液,最后注入聚合物顶替液、替清水,关井成胶再后续水驱。在 4 个井组开展了现 场试验。取得了较好的开发效果,主要表现在以下几个方面: 一是调剖后注入压力明显上 升,油层渗流能力下降; 二是调剖后吸水指示曲线拐点消失,启动压力抬升,说明裂缝得 到了封堵;三是根据 4 口深调井调剖前后吸水剖面资料分析,主要目的层注水得到控制,非 目的层注水得到加强; 四是从生产井采出液水质分析结果证实, 交联聚合物体系分子已在高 渗透段的孔隙中产生物理堵塞,提高了注入压力,扩大了波及体积,提高了油层动用程度。 深调后 9 口目标井调剖后日增油 8.3t,含水下降 11.9 个百分点。目前试验区已累积增油 1508.5t,累积降水 8070 m3,现仍处在有效期中。通过经济效益分析,截止到目前,投入产 出比为 1:1.73。并且该区与调剖前相比,仍保持着增油降水的开发形势,深调还处在有效期 中。从室内及现场试验中可以得出以下结论: 1、通过室内实验,优选出了适合朝阳沟油田 一类区块的调剖剂配方。 该配方所形成的交联体系与地层水和注入水具有较好的配伍性、 热

稳定性和较强的流变性。 应用上述配方配制的聚合物交联剂混合溶液模拟地层条件, 能够形 成凝胶,对岩心中的裂缝进行有效封堵,后续水进入岩心基质部分,增大波及体积,提高基 质部分原油采收率。 2、通过数模研究计算,确定了适合朝阳沟油田一类区块的深度调剖各 项技术参数。 3、 本篇论文优选的调剖剂配方和技术参数在朝阳沟油田裂缝性低渗透油藏应 用是可行的,可以满足现场注入的要求。 4、 深度调剖是改善中高含水期开发效果的一项 有效的技术手段, 调剖剂对裂缝和高渗透层起到了一定的封堵作用, 油层动用状况得到改善, 见到较好增油降水效果。 Chaoyanggou Oilfield belongs to fractured low-permeability reservoir . The fracture density of first type tracts of the oilfield host body is 0.13 strip/m. After 17 years of waterflood development , the present recovery percent of reserves attains 20%, comprehensive water content is 48.7%. Because of finger advance nonhomogeneity , the interlayer and plane incensistence increase, water content rises continuously, and there is little room for the injection. It interlayer and plane inconsistence increase, water content rises continuously ,and there is little room for the injection-production system to be adjusted after linear water injection . It is difficult to adjust and exavate with conventional technical methods .In order to improve the development result further and enhance the recovery ratio , We has carried out the deep profile control research. It can seal fractures and high-permeability zones effectively. Make succeeding water enter the matrix and expand the swept volume, alleviate interlayer and plane inconsistence and improve the development result . According to the reservoir condition , we consider mainly the pore structure and fracture feature of low-permeability reservoir ,we has carried out the formula optimum of the profile control agent、property evaluation 、core sealing and oil displacement test after sealing、 nuclear magnetic resonable image formation research and the sealed environment of gel to fracture eectronic lens scan microscopic test research . We optimized the profile control agent formula which is compatible with the Chaoyanggou reservoir. The profile control agent is made up of main agent 、cross-linking agent and addition agent . The main agent is HPAM . The primary material of the cross-linking agent is chlorinated chromium. The addition agentg is mainly thiourea. The polymer used for deep profile control is partly hydrolytic PAM. Its molecular weight is 14 million. Its degree of hydrolysis is 25%. The lab simulation test shows, with the increase of the concentration of polymer, the solution initial viscosity and gelation viscosity increase. Considering gelation viscosity and praltical injection capability, we determin the proper polymer concentration is 800-1200mg/l. Through the test of different cross-linking ratio of the oraganic chromium system’s effect on gelation property, we conclude: with the increase of the cross-linking ratio ,the gel viscosity increase. Considering gelation viscosity and economic benefit, we determine the proper cross-linking ratio is 15:1. The test shows NaCl and NaHCO3 can adjust the cross-linking velocity. With the increase of the concentration, the cross-linking reaction gets faster. After screening, 600-800mg/l NaCl and 500-750mg/l NaHCO3 are proper. We use thiourea as the stabilizer of the formula gel. Its optimal concentration is 1000mg/l. The lab test shows, the cross-linking system is well compatible with the formation water and the injected water. The profile control agent has been diluted by the formation water before gelation. It also has good stability and mobility control capability. The oil displacement test of the natrual core with fractures shows, when water flooding gets residual condition, the gel seals the cores, the succeeding water flooding core recovery ratio can be increased by 6.3 to 9.1 percent. The result of nuclear magnetic resonance and microscopic emulation model test shows: the polymer and cross-linking agent mixed solution migrates through fractures after entering the model, packs the fractures, forms sealing function on fractures after gelation, forces succeeding injected water

change liquid stream direction. And it enters the matrix of the model. With the succeeding water flooding, the swept volume is expanded. And it makes stable crude oil before packing in matrix migrate. Crude oil is displaced at model outlet. Thus the recovery ratio of crude oil is enhanced. The scanning electronic lens result of the sealing environment of gel on core with fractures shows: gel has better sealing function on fractures of fractured reservoir. At the some time, the gel entering into matrix decreases. This warrants that the matrix can not be packed by gel. And the succeeding water can flow through matrix, thus enhances the recovery ratio. We have built up plane geological model according to the geological and fluid feature of Chaoyanggou oilfield. The result of simulation calculation shows that sealing radius of 1/5~1/3 well spacing of high-permeability strips has better result. The plan that the injected gel slug size is 0.02~0.04PV is optimal. The injection chance of different water content affects oil displacing result heavily. Sealing result is optimal when water content is 70%~80%. At the same injection volume of gel slug, in order to avoid profile control solution being diluted, we adopt various ways of slug injection. We inject a certain volume preflush first, and then inject profile control solution from low to high concentration, inject polymer displacing liquid, removal water at last, and close well for gelation before succeeding water flooding. We have carried out field test of 4 well groups. It obtained better developing result, as following: The first is that the injection pressure increases obviously and the percolation capability of reservoir decreases; The second is that the flex point of water absorbing indication curve disappear and the starting pressure increases. It illustrates that the fracture are packed; The third is that water injection of interval of interval of interest is controlled and that of other layers is enhanced according to analysis of the absorption profile data for 4 deep prlfile control wells before and after the profile control . The fourth is that the result of produced liquid water quality verifies that the cross-linking polymer system molecules form physical plugs at high- permeability interval pores , it increases injection pressure ,expands swept volume and enhances producing extent of reservoir. After deep profile control the daily oil increment of 9 target wells is 8.3t ,the decrease of water content is 111.9 percents. The cumulative oil increment of the pilot area is 1508.5t and cumulative water decrease is 8070m3 . And they are still at valid period . Through the analysis of economic benefit , up to now, the input-output ratio is 1:1.73. The tract keeps the development situation of oil increasing and water decreasing after measurement. It is still at valid period. The conclusions from lab test and field test are as following: 1. polymer cross-linking agent mixed solution forms gel, it packs the fractures of cores effectively, this makes displacement pressure increases dramatically, permeability of fractures decreases heavily. This expands the swept volume and enhances the recovery ratio. 2. Different tracts and geological conditions have different technical parameters at deep profile control. 3. The formula of profile control agent and technical parameters optimized by the paper is feasible at the fractured low-permeability reservoir of Chaoyanggou Oilfield. And it can satisfy the practical injection. 4. The deep profile control is a effective technical method to improve the development result of middle and high water content period. The profile control agent packs the fractures and high-permeability layers to some extent. The reservoir producing condition is improved. And it has better result of oil increasing and water decreasing. 本 文 来 自 : 聚 合 吧 (http://www.juhe8.com/) http://www.juhe8.com/lunwen/qita/2008-01-14/86958.html 详 细 出 处 参 考 :


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