【作者】 肖丹凤；

【导师】 刘合； 朱君； 王尊策；

【作者基本信息】 东北石油大学 ， 油气田地面工程， 2010， 博士

【摘要】 大庆外围低渗透储层是目前油田产量接替的主要开发调整对象,低渗透储层必须通过压裂改造才能投入开发。由于该类油藏储层物性差,压裂过程中,储层极易受到伤害,如何有效控制和降低压裂过程对储层和人造导流裂缝渗透率的损害,提高单井产量,是大庆外围低渗透储层压裂改造时必需要面对的严峻挑战;大庆海拉尔油田岩性复杂、储层物性条件差,压裂中经常出现低砂比时砂堵,甚至出现压不开的情况,提高施工成功率,是海拉尔油田开发必须要解决的关键问题。利用红外、核磁、激光光散射、黏度等实验手段,对新型多侧基植物胶的结构和分子量进行表征。新型多侧基植物胶的分子结构是由半乳糖和甘露糖组成,半乳糖与主链上甘露糖的比值为1:1.34,明显高于胍胶的1:1.67。新型多侧基植物胶的分子量为5×105,显著低于常规用胍胶的分子量。由于新型多侧基植物胶分子量较低,并且含有更多的侧基,其空间位阻效应增加了高分子链的刚性,阻止了溶液中植物胶因分子间氢键相互作用产生聚集,因此新型多侧基植物胶水溶性更好,水不溶物含量更低,是一种比胍胶性能更加优越的压裂液增稠剂。利用新型多侧基植物胶为增稠剂制备了新型多侧基植物胶压裂液并且和羟丙基胍胶压裂液进行了对比和分析。在相同剪切粘度和温度条件下,新型多侧基植物胶的使用浓度要比羟丙基胍胶降低近30%,残渣含量比常规羟丙基胍胶压裂液降低45%左右,降低了对储层和人造导流裂缝渗透率的损害,适合对低渗透储层进行压裂增产改造。利用小幅振荡剪切实验得到的平台模量Gp和零切粘度η0结合起来对压裂液的网络结构和性能进行评价,并且对不同交联剂类型、浓度、不同多侧基植物胶浓度以及多侧基植物胶交联液和羟丙基胍胶交联液的流变性能进行对比和分析。优化和筛选出分子尺寸以及与硼离子络合能力不同的两种有机分子,通过控制反应条件制备出复合型有机硼交联剂,利用空间位阻效应和逐级释放技术提高了硼离子稳定性和延缓释放的时间,使压裂液的成交时间达到延缓可控,提高了压裂液冻胶的耐温和耐剪切性能。采用延缓交联新型多侧基植物胶压裂液,大幅度降低了压裂液施工时的沿程管路摩阻,提高了压裂施工成功率。优化了新型多侧基植物胶压裂液的整体性能,通过引入阳离子型低分子量和多支化度的聚二甲基二烯丙基氯化铵类高分子,利用其高分子链上的正电荷把不同的粘土颗粒结合在一起,可以有效抑制粘土破碎、脱落和运移;通过将含类表面活性剂与氧化铵类表面活性剂相结合,在降低表界面张力的同时增加了接触角,从而大幅度降低了毛细管力,显著提高了压裂液的返排性能。利用新型多侧基植物胶压裂液在大庆外围油田低渗透储层油井中共应用了576口井1719个层,压裂施工成功率达97.0%,压裂后初期平均单井日产液3.19m3/d。低损害新型多侧基植物胶压裂液有效解决了低渗透储层压裂液伤害问题。利用延缓交联多侧基植物胶压裂液技术,对大庆海拉尔油田深部高含泥南屯组储层进行了压裂改造,现场试验52口井89层,储层平均深度2634.9m,施工成功率为96.6%,压后初期平均单井产液10.84 m3/d。通过现场下入井底压力计对比测试结果表明,利用延缓交联压裂液技术,压裂液的沿程摩阻下降了5.7MPa以上,由此在不改变地面压裂施工设备的条件下,有效解决压裂中经常导致低砂比时砂堵,甚至出现压不开的情况,施工成功率由原来的百分之八十左右,提高到百分之九十六以上,有效解决了深部南屯组高含泥储层压裂成功率低难题。到目前为止,新型多侧基植物胶压裂液628口井1808个层,成功率达96.96%,压裂后平均单井增油量为2.65t/d,比常规羟丙基胍胶压裂液的增产效果提高了133%,改善了压裂增产效果,满足了低渗透油田开发需要。更多还原

【Abstract】 The low permeability reservoirs in the peripheral oil fields are the main reservoirs for increasing production in Daqing fields. It must be fractured before being put into development. The formation is easy to be damage in the process of fracturing due to the poor reservoir properties and vulnerable. How to control and reduce the formation and man-made crack damage effectively during the fracturing process, and how to enhance the well productivity of this low permeability reservoir are the serious challenges we have to face. In addition, Hailar oilfield of Daqing has complex lithology and poor physical condition. Sand plug occers occasionally, even if the proppant concentration is low during the fracturing process. How to improve the success rate of fracturing treatment is the key issue which must be solved for Hailar oilfield fracturing stimulation.The structure and molecular weight of the novel vegetable gum (VG) with many side groups are characterized using IR, NMR, light scattering, viscosity and other experimental methods. The molecular structure of this novel VG is also composed of galactose and mannose unit. The ratio of side galactose groups with mannose on main chain is 1:1.34, significantly greater than ordinary guar gum with the raio of 1:1.67.The molecular weight of this novel vegetable gum is 5×105, significantly lower than the molecular weight of ordinary guar gum. The steric effect makes the rigidity of the polymer chain increase accordingly due to the reason that new VG has more side groups. As a result, the intermolecular aggregation of the novel VG chains through the hydrogen bonding is prevented. This explains why this novel VG has the better water-soluble performance and lower water insolubles so that thickening behavior is much better than ordinary guar gum.Based on this new gum, a novel fracturing fluid is developed and the performance of that is studied and compared with the hydroxypropyl guar (HPG) aqueous solution. In the conditions of the same shear viscosity and temperature, the usage amount or concentration of VG is lower than HPG by nearly 30%,and the residue content of this novel fracturing fluid is nerely 45% lower than that of HPG based fracturing fluid. Therefore, it reduces the damage of both reservoirs and man-made crack, which on the needs and satisfaction of the fracturing treatment on the low permeability reservoirs.The paper also present the criterion by which the performance of fracturing fluid can be determined by using the combination of platform modulus Gp and zero shear viscosityη0 obtained by the small oscillation shear experiments. This paper also studies the performance of this novel fracturing fluid at different crosslinker concentrations and different VG concentrations and compares it with the performance of HPG based fracturing fluid.By optimizing and selecting two different organic molecules which have different molecular sizes and different complex capacity with boron, together with controlling the reaction conditions, a novel boron based crosslinker is synthesized. The crosslinking time of fracturing fluid may be delayed and controllable due to the steric effect and sequential release technology, the performance of boron based crosslinker, including the stability, resistance to the high temperature and shear rate, enhances significantly. The pipeline friction is dropping rapidly along the fracturing process and improve the success rate of fracturing process by crosslinker with the novel VG thickener,We also optimize the overall performance of this novel VG fracturing fluid. By introducing the cationic polyelectrolyte with the low molecular weight and multi-degree of branching such as polydimethyldially ammonium chloride, the positive charges along the polymer chains can combine different clay particles, and then inhibit the clay particles form breaking, losing, and migrating. By combining surfactants of oxidation of ammonium with the surfactants containing fluorine, the surface and interface tension reduces whereas the contact angle increases signifacntly. As a result, the capillary force becomes nerely zero, improving the flowback ability and other performances of fracturing fluid significantly. In addition, in this paper we also optimized demulsifiers, fungicides, soluble fluid filtration additive, capsule breaker to endue fracturing fluid better anti-emulsifying, anti-metamorphic, lower fluid filtration and gel breaking performance.By using the novel plant gum fracturing fluids with many side groups, we carry out fracturing treatment in 1791 zones 576 wells in low permeability reservoir of daqing peripheral oilfields, the fracturing operation success rate is 97.0%, the average daily fluid production of single well in the early stage after fracturing is 3.19m3/d. Based on the novel fracturing fluid technique, the formation damage problem during fracturing process which treats on low permeability reservoirs of the peripheral oil fields of Daqing can be solved effectively.By using this novel fracturing fluid, the fracturing treatment is carried out on reservoirs which are deeply buried and have high mud content conditions in Hailaer oifield. Accumulated in 52 wells, about 89 layers, the average reservoir depth is 2634.9m, the success rate and the average liquid production is 96.6% and 10.84 m3/d respectively. Base on the contrast testing with the bottom-hole pressure device, the results show that by using the delayed crosslinking fracturing technique, the pipeline friction of fracturing fluid reduces at least 5.7 Mpa. Without changing the conditions of fracturing equipments on the ground,the sand plug during fracturing treatment process with low proppant concentrations and even the failure to fracturing the reservior can be solved. The success ratio of fracturing increases from about 80% in the past to at least 96% at present. Based on the novel fracturing fluid technique, the success rate of fracturing treatment on high mud content reservoirs in Hailaer oil field can be improved effectively. So far, a number of wells are treated by this novel VG based fracturing fluid is 628, about 1808 layers .The success rate is up to 96.96%. The average well productivity is 2.65t/d. The efficiency of the production enhancement treated by this fracturing fluid is 1.33 times higher than that treated by conventional HPG based fracturing fluid. The application of this new technology will reduce formation damage due to fracturing fluid filtration and improve fracturing stimulation effect and economic benefits significantly, which have met the needs of developing low permeability oil fields.更多还原