Optimization of the Algorithm for Increasing Injection Rate in Water Injection Wells for Pressure Optimization in P Oilfield

In today’s society, with the continuous growth of energy demand, Bohai Oilfield, as an important offshore oil resource base in China, is facing increasingly severe challenges while contributing to national energy security. In order to improve the quality of water injection in the oilfield and gradually achieve efficient and stable production, Bohai Oilfield has launched a water injection well pressure optimization project, focusing on improving the efficiency and quality of water injection in the water injection wells, in order to achieve the optimal water injection plan. In practical work, P Oilfield continues to promote the development of water injection well pressure optimization projects, emphasizing practical exploration and continuous optimization of work plans. However, during the project implementation process, there were some problems, one of which was that the statistics of cumulative injection volume were not scientific enough, resulting in a more comprehensive and accurate presentation of the actual results of pressure optimization work. In the context of continuous improvement work, after careful analysis and research, P Oilfield has decided to optimize the cumulative injection rate algorithm to guide the oilfield’s water injection work in a more refined way, ensuring sufficient and good water injection, and enhancing the oilfield’s production efficiency and comprehensive competitiveness.

Three-dimensional physical simulation and optimization of water injection of a multi-well fractured-vuggy unit

With complex fractured-vuggy heterogeneous structures, water has to be injected to facilitate oil pro- duction. However, the effect of different water injection modes on oil recovery varies. The limitation of existing numerical simulation methods in representing fractured- vuggy carbonate reservoirs makes numerical simulation difficult to characterize the fluid flow in these reservoirs. In this paper, based on a geological example unit in the Tahe Oilfield, a three-dimensional physical model was designed and constructed to simulate fluid flow in a fractured-vuggy reservoir according to similarity criteria. The model was validated by simulating a bottom water drive reservoir, and then subsequent water injection modes were optimized. These were continuous （constant rate）, intermittent, and pulsed injection of water. Experimental results reveal that due to the unbalanced formation pressure caused by pulsed water injection, the swept volume was expanded and consequently the highest oil recovery increment was achieved. Similar to continuous water injection, intermit- tent injection was influenced by factors including the connectivity of the fractured-vuggy reservoir, well depth, and the injection-production relationship, which led to a relative low oil recovery. This study may provide a constructive guide to field production and for the devel- opment of the commercial numerical models specialized for fractured-vuggy carbonate reservoirs.

TWO-PHASE FLOW FOR A HORIZONTAL WELL PENETRATING A NATURALLY FRACTURED RESERVOIR WITH EDGE WATER INJECTION

This paper examines the two-phase flow for a horizontal well penetrating a naturally fractured reservoir with edge water injection by means of a fixed streamlinemodel,The mathematical model of the verical two-dimensional flow or oil-water for a horizontal well in a medium with double-porosity is established ,and whose accuratesolutions are obtained by using the characteristic method .The saturation distributionsin the fractured system and the matrix system as well as the formula of the time of water free production are presented .All these results provide a theoretical basis and a computing method for oil displacement by edge water from naturally fracturedreservirs.

Study and application of a new blockage remover in polymer injection wells

With the extensive application of polymer flooding technology in offshore oilfields,the plugging in polymer injection wells has become more and more severe,which seriously affects the oil displacement effect and regular production of oilfields.In this paper,a new kind of blockage remover has been developed and evaluated by rheological behavior experiments,dissolution experiments and core flooding experiments.The results reveal that this new blockage remover can effectively reduce the viscosity of polymer and completely degrade the reservoir blockage with low corrosion rate.It is beneficial to long-term production of oil wells in offshore oilfield.Results of core flooding experiments show that this new blockage remover can relieve polymer damage and improve permeability.The agent has been applied in LD10-1 oilfield in 2016,the daily injection rate increased significantly after stimulation.

Investigation of the performance of a pilot-scale barrel atmospheric plasma system for plasma activation of polymer particles

This study reports the development and performance of a pilot-scale barrel atmospheric plasma reactor for the atmospheric plasma activation treatment of polymer particles. The polymer particles treated included acrylonitrile butadiene styrene(ABS) and polypropylene(PP). These particles had diameters in the range of 3–5 mm. The initial studies were carried out using a laboratory-scale barrel reactor designed to treat polymer particle batch sizes of 20 g. A pilot-scale reactor that could treat 500 g particle batch sizes was then developed to facilitate pre-industrial-scale treatments. The effect of operating pulse density modulation(PDM) in the range 10%–100% and plasma treatment time on the level of activation of the treated polymers were then investigated. ABS revealed a larger decrease in water contact angle compared with PP after plasma treatment under the same conditions. The optimal treatment time of ABS(400 g of polymer particles) in the pilot-scale reactor was 15 min. The plasma-activated polymer particles were used to fabricate dog-bone polymer parts through injection molding.Mechanical testing of the resulting dog-bone polymer parts revealed a 10.5% increase in tensile strength compared with those fabricated using non-activated polymer particles.

Application of Polymers in Low Permeability Formations

For low-permeability sandstone reservoir with big channel, we researched the novel deep profile method alternative injection of anionic and cationic polymer. Evaluating various factors on adsorption capacity through lab test, the results show that with the increase of temperature, the adsorption capacity decreases and the cationic polymer is easier to be absorbed. With the increase of salinity, adsorption time or polymer concentration, the adsorption capacity increases. The adsorption equilibrium concentration of cationic polymer is 1500 mg/L;adsorption equilibrium time is 8 h. The adsorption equilibrium concentration of anionic polymer is 1000 mg/L;adsorption equilibrium time is 6 h. Physical simulation experiment shows that alternative injection of anionic and cationic polymer is better than injection of single polymer, and preferential injection of cationic polymer is better than preferential injection of anionic polymer. With the increase of injection rounds, sealing capacity gets better, but in view of cost, the rounds should not be more than 3. The profile control technique can obviously enhanced oil recovery, and water displacement recovery increases 41%. 2 wells were tested successfully in Henan Oilfield in June 2010. Approximate 154.47 tons of incremental oil was obtained with 2% water-cut decrease.

Experiments on the influences of well pattern on water flooding characteristics of dissolution vug-cave reservoir

Based on the similarity criterion, volcanic rock samples were taken from outcrops to make experimental models. Water flooding experiments of five-spot well pattern, nine-spot well pattern, five-spot to nine-spot well pattern, the relationship between relative well and fracture positions, and injection rate in dissolution vug-cave reservoirs with/without fractures were carried out to analyze variation regularities of development indexes, find out development characteristics of water flooding with different well patterns and sort out the optimal water flooding development mode. For dissolution vug-cave reservoirs without fractures, five-spot well pattern waterflooding has very small sweeping area, serious water channeling and low oil recovery. When the well pattern was adjusted from five-spot to nine-spot well pattern, oil recovery could be largely improved, but the corner well far from the injector is little affected. In dissolution vug-cave reservoirs with fractures, when the injector and producer are not connected by fractures, the fractures could effectively connect the poorly linked vugs to improve the development effect of water flooding. Whether there are fractures or not in dissolution vug-cave reservoirs, the development effect of nine-spot well-pattern is much better than that of five-spot well pattern and five-spot to nine-spot well pattern, this is more evident when there are fractures, and the edge well has better development indexes than corner well. At the high-water cut stage of water flooding with nine-spot well pattern, the oil recovery can be further improved with staggered line-drive pattern by converting the corner well into injection well. It is helpful to increase the oil production of corner well of nine-spot well pattern by increasing the injection rate, and improve ultimate oil recovery, but the water-free production period would be greatly shortened and water-free recovery would decrease.

平衡式双解封注水封隔器的研制与应用

针对冀东油田大斜度深井多级分注管柱解封负荷大、密封有效期短的问题,在剖析封隔器结构的基础上,对关键结构进行三维仿真模拟优化设计,研制了平衡式双解封注水封隔器。该封隔器设计独立的双解封方式,减小解封负荷;利用弹簧及注水管柱内外压差,实现反洗阀自动关闭;综合采用橡胶挤压及金属线密封方式,提高反洗阀密封可靠性;胶筒优选高强度氟橡胶材质,提高耐温耐压性能;设计平衡活塞保护解封销钉,消除高压差提前解封风险。现场应用11井次,施工成功率为100%,密封有效期超过30个月;起管解封负荷降低17.2%。该封隔器密封周期长,解封负荷小,可满足大斜度深井高压分注长效密封需求,具有良好的经济效益和推广应用前景。

大庆油田二类B油层聚驱剖面动用规律及其改善

大庆油田聚合物驱应用规模不断扩大,开发对象转向性质较差的二类B油层,现有聚合物与油层适应性不强,剖面动用规律不明确,不同地区聚驱开发效果差异较大。针对上述问题,应用矿场剖面数据统计和室内实验分析,研究了二类B油层剖面动用规律和剖面改善方法。结果表明:从吸水层动用情况来看,喇嘛甸地区由于发育厚层河道砂,油层物性好,油层有效厚度动用比例最高,油层以多次动用为主,突进层多,相对吸液量高;萨中和萨南地区河道砂发育规模小,薄砂层较多,物性差,有效厚度动用比例较低,但聚驱后,有效厚度动用比例相比水驱分别增大了12.5%和15.4%,渗透率为100~300 mD的储集层吸入剖面改善明显;从未吸水层动用来看,二类B油层纵向非均质性强,导致层间有效厚度未动用比例较高,剖面改善应以均衡层间动用为主;抗盐聚合物高、低质量浓度交替注入可延缓含水率上升时间,增加低渗透层吸液量,聚驱采出程度提高显著。在喇嘛甸北北块A区开展了DS1200抗盐聚合物和高、低质量浓度交替注入试验,降水增油效果好,可为大庆油田二类B油层聚驱剖面改善提供技术指导。

注水井作业用压井液体系的构建及应用

针对压井液存在易污染地层,降低储层渗透率,压井作业风险大等问题,研究了一种密度在1.3~1.7 g/cm^(3)范围内可控的压井液体系,通过对压井液中各组分的筛选,确定了压井液的基本配方为:饱和盐水(NaCl)+1.5%~2.5%VI-F+1.0%~2.0%WET+3%PG-6+0.1%HY-3+B280。压井液的综合性能评价结果表明:压井液体系防膨率>95%,损害率<8%,滤失量<10 mL,表观黏度≤100 mPa·s,15 d内无沉降分层,具有良好的稳定性;现场试验表明,该压井液体系与地层配伍性良好,可实现有效压井作业,且对储层伤害性较小。

延迟成胶弹性硅酸凝胶堵水剂及其性能研究

针对现有硅酸凝胶堵水剂普遍存在成胶时间短、成胶后脆性大的问题,结合L油田油藏条件,通过考察活化剂类型及用量,弹性改善剂类型及用量,以及水玻璃用量对成胶时间和弹性模量的影响,得出了一种延迟成胶弹性硅酸凝胶堵水剂。其配方为:6%水玻璃+0.85%活化剂三元弱酸一铵GL-1+0.1%弹性改善剂正电胶,该配方在油藏温度65℃下,成胶强度达到E级的时间为72 h,成胶后的弹性模量为589.46 Pa。采用填砂管实验评价了堵水剂的注入性及封堵性,结果表明堵水剂在L油田中具有良好的注入性及封堵性,在渗透率为1168.06×10^(-3)~5061.57×10^(-3)μm^(2)的填砂管中,注入0.8 PV的最高注入压力仅有0.72 MPa,封堵率均>96%。该堵水剂可用于L油田的油井堵水。

压裂水平缝水平井邻井注水补充地层能量机理研究

文章针对浅层低渗透油藏压裂水平缝水平井开发过程种出现的产量递减快,能量补充技术缺乏,水窜治理技术欠缺的问题,开展实施邻井注水补充能量的可行性分析与设计优化研究。首先对目标油藏目前实施的水平井邻井注水补充能量实例的实施情况与效果及存在问题进行剖析,然后综合油藏工程与数值模拟技术对邻井注水补能过程中的关键因素及其作用规律进行了研究;最后确定了该技术实施的原则与技术政策。

适合延长油田低渗透储层分层注水井的有机酸解堵体系

为了解决延长油田低渗透储层分层注水井注入压力升高以及注水量下降的问题,以复合有机酸FH-S为主体酸液,结合黏土稳定剂、缓蚀剂和助排剂等主要处理剂,研制了一套适合延长油田低渗透储层分层注水井的有机酸解堵体系,室内对其基本性能和岩心驱替解堵性能进行了评价。结果表明:有机酸解堵体系具有良好的溶蚀性能、缓蚀性能和较强的铁离子稳定能力,降低表面张力和界面张力的效果也较好,体系与地层水的配伍性较好,不会出现浑浊和沉淀;另外,在天然岩心被注入水污染后挤入2 PV有机酸解堵体系,能够有效解除堵塞污染,岩心驱替压力明显降低,岩心渗透率恢复值可以达到100%以上,解堵效果较好。现场应用结果表明:目标注水区块5口注水井采取有机酸解堵体系施工措施后,注入压力显著降低,日注水量明显增大,并且措施的有效期较长,取得了良好的现场施工效果。

致密油藏大排量注水吞吐技术及参数优化研究

针对致密油藏水平井自然渗吸采收率低和长期衰竭开发后期地层能量如何补充的难题,在储层基本特征、致密油藏注水吞吐采油机理的基础上,提出了大排量水平井注水吞吐。以鄂尔多斯盆地长7段致密油藏为研究对象,选取天然岩心和人造岩心相结合方式,利用核磁共振等方法,通过室内注水吞吐实验研究了自然渗吸和不同注水速度下吞吐动态渗吸的作用范围和微观孔隙动用特征,分析了排量对孔隙动用情况的影响,并开展了焖井时间影响实验,最后利用数值模拟方法对压裂水平井注水吞吐开发的注水量、焖井时间参数进行优化。研究表明:小排量时,注水吞吐主要动用的是大孔隙,中小孔隙动用较低;大排量时,注水吞吐不仅动用了大孔隙,且中小孔隙动用明显提高,使得整体的采收率出现较大增加。随着焖井时间的延长,油水置换作用越充分,使得注水吞吐采出程度越高,但其提高的程度逐渐稳定。对A9井进行数值模拟优化,得到最佳日注水量为900 m^(3),最佳焖井时间为24 d,在矿场试验取得成功,初期日增油2.11 t,有效期365 d,累计增油770 t。

大庆油田调整井固井技术研究

大庆油田经过多年的调整开发,受地层非均质性、井网加密、动态注采开发等影响,已改变了原始井下环境。针对大庆油田异常高压层油水侵、高渗低压层界面胶结质量差两方面难题,以“地质先行,一井一策”为指导思想,开展了钻井地质、水泥浆体系、固井工具等技术攻关,形成注水开采油田调整井固井配套技术。现场应用取得了良好效果,为大庆油田原油产能建设提供井筒保障。

周长南部致密油常规井注水开发论证分析与研究

为实现吴起油田的持续、快速、稳定发展,需要制定合理的注水开发政策。对周长南部区域的致密油常规井注水开发进行论证分析,采用油藏数值模拟技术和经验公式等方法确定了合理的注水方式、注水周期、注水量以及注水压力,以最大程度地提高开采效果,降低含水率,进而为致密油藏的高效开发提供了理论支持,从而为延长油田的寿命和提高产能提供科学依据。

桥式同心配水器结构优化及其在南堡油田的应用

南堡油田注水开发已处于油藏中后期,为满足油藏“注上水、注够水”的开发需求,大斜度井分注需求逐年增加。此前,大斜度井采用同心分层注水工艺技术后,存在调不动和漏失量大等问题。针对同心配水器存在的问题,对水嘴形状和结构进行优化改进,开展模拟测试并应用于矿场试验。该技术已在油田58口井上成功应用,应用井的最大井斜62.08°,施工成功率100%,初次测调成功率100%,测调效率提升2倍。

渤海油田化学驱注入井解堵剂构建、性能和注入工艺

渤海J油田经历长期化学驱,注入井储层低渗透部位堵塞严重,常规解堵措施效果较差,亟待开发新型解堵剂和解堵工艺。为此,以渤海油田目标油藏聚合物驱水井返排堵塞物为研究对象,开展了化学驱注入井解堵剂构建、性能评价和工艺研究。结果表明,目标油田化学驱水井返排堵塞物由87.77%水、3.83%原油、2.76%聚合物和5.64%无机垢构成,其中无机垢主要包括59.1%SiO_(2)、25.9%CaCO_(3)和11.4%MgCO_(3),同时含有少量的BaCO_(3)、SrCO_(3)、BaSO_4、SrSO_4和Fe_(2)O_(3)。根据堵塞物成分,构建了由有机溶剂、解聚剂和溶垢剂等组成的新型解堵剂。优选出的有机溶剂为甲苯与正戊醇的混合物(质量比9∶1~7∶3),解聚剂为0.5%~1.0%过硫酸铵,溶垢剂为5.46%溶垢剂1(α-环糊精包合体和β-环糊精包合体)+0.54%柠檬酸。3种类型解堵剂依次加药的溶垢效果好于复配加药方式,按解聚剂+有机溶剂+溶垢剂(质量比为1∶2∶3)的加药顺序,对堵塞物的溶垢率为98.1%。岩心解堵实验结果表明,新型解堵剂对无机混合垢和聚合物堵塞的解堵率超过80%。与单独解堵作业相比,无机凝胶调剖+解堵联合作业兼具“堵”和“疏”双重功效,采收率增幅提高6.9百分点。