【作者】 杨希志；

【导师】 王德民；

【作者基本信息】 大庆石油学院 ， 油气田开发工程， 2008， 博士

【摘要】 本文在国内外有关聚合物驱、表面活性剂降压增注等基础理论文献的基础上,对聚合物粘弹性、渗流力学和高浓聚合物驱提高采收率、表面活性剂降压增注机理等方面内容进行了系统的研究。同时,结合这些理论进行了高质量浓度聚合物驱油方法、表面活性剂降低高浓聚合物注入压力实验研究、高浓聚合物矿场低压注入方案研究及效果评价等具体工作。本文的研究成果对提高高浓聚合物注入能力、拓展聚合物工程实践和丰富高浓聚合物驱油理论研究,具有重要的学术理论意义和工程实际应用意义。全文的研究共分四个部分,下面分别作简要叙述:1、聚合物溶液的粘弹特性本部分进行了聚丙烯酰胺和黄原胶溶液的粘弹性的实验测试研究,并且对影响粘弹性因素(溶液质量浓度、配制水矿化度及分子量)进行了实验测试。本节的主要目的是根据稳态剪切实验和动态力学实验,揭示出HAPM与黄原胶溶液粘弹特性的差异及各影响因素对溶液粘弹性的影响规律。研究表明:HPAM的第一法向应力差的大小与HPAM溶液的质量浓度、分子量和矿化度有关;HPAM的法向应力差N1随着溶液质量浓度、分子量的增加或矿化度的减小而增加;黄原胶溶液的法向应力差N1随着随剪切速率的增加,呈波动下降趋势。通过对比,黄原胶溶液是具有储存模量和低法向应力差的粘弹性流体。HPAM溶液弹性粘度/剪切粘度与剪切速率之间具有较好的线性关系;在油层流速条件下,聚合物溶液出现拉抻流动。2、高质量浓度聚合物驱油方法的室内实验和矿场试验研究室内岩心驱油实验结果表明,高质量浓度聚合物驱转注时机越早;或质量浓度越高、或分子量越高,都能够使采收率比水驱提高20%OOIP左右,增加采收率的幅度与三元复合驱相当,但其费用比三元复合驱低。2002年8月,在大庆油田6口注聚井(3口高渗井,3口低渗井)进行高质量浓度聚合物注入能力试验,其油层有效渗透率范围0.354~1.06μm2。试验结果表明:高渗透率油层(K≥0.890μm2 )可以实现高质量浓度(2000mg/L ~2500mg/L,粘度200 ~ 250 mPa.S)聚合物的连续有效注入。2003年9月,6口分散注聚井周围油井平均单井日产液94.2吨,平均单井日产油23.7吨,平均含水率为74.9%,与注入浓度为1000mg/L聚合物溶液相对比,平均单井日产液稳定,平均单井日产油上升6.2吨,增幅为35.4%,平均含水率下降6.6%。结果表明,高质量浓度聚合物溶液的注入是有效的。3、表面活性剂降低高浓度聚合物注入压力室内实验以及作用机理的研究室内降压结果表明:在注入氧化剂和注入1.0倍孔隙体积NOS表面活性剂体系后,使后续高浓度聚合物溶液驱替压力下降了47.86%~67.01%,连续注入90.0倍孔隙体积左右后,注入压力不回升;NOS体系的界面张力越低,高浓度聚合物溶液的注入压力越低。表面活性剂降低高浓聚合物注入压力的原理是:(1)先注入氧化剂溶液将砂岩孔道上吸附的聚合物膜脱除;(2)表面活性剂洗掉油层中的部分残余油以提高了油层的渗透率,实验证明:可动油饱和度明显增加,残余油饱和度降低,油、水等渗点发生右移,扩大了油、水两相共渗区;(3)注入的表面活性剂可在砂岩孔道表面形成一个吸附层,相对于聚合物吸附层厚度很小,因此对渗透率的影响很小,并且表面活性剂分子可以防止聚合物分子再次形成新的厚聚合物膜,从而保持渗透率不再下降。4、降低高浓度聚合物注入压力矿场试验研究和效果评价6口单井试验结果证明:采用表面活性剂降压和树脂砂压裂技术,可以降低高浓聚合物注入压力,增注后的降压幅度和增注量可以满足注入量和将注入压力降到破裂压力以下的要求。对于渗透率较高的地层,表面活性剂降压效果更好。采用表活剂的增注有效期是常规压裂的2倍以上。对隔层比较好、并且需要单层增注的井,应该选用树脂砂压裂工艺;对隔层不好、或者需要多层增注的井,应该选用活性剂降压工艺。现场区块试验结果表明,高浓度、高分子量聚合物驱可以突破采收率增加值是12%左右的界限而达到18~24%左右,而且聚合物浓度越高,采收率进一步提高的幅度越大,说明了注高浓度聚合物溶液可以进一步提高采收率。更多还原

【Abstract】 According to the investigation actuality of the basic theory study on polymer flooding,surfactant solution decrease pressure of injection and increase ability of injection, this paper study systemically on viscoelasticity of polymer, permeability mechanics and enhance oli recovery, surfactant solution decrease pressure of injection and increase ability of injection. Base on result studied, high-concentration polymer flooding and surfactant solution decrease pressure of injection and increase ability of injection was studied at the same time. The results of the study are significant to enrich the basic theory study of relative fields and accelerate development of these subjects.The research results of the paper can be divided into four special topic, which will be briefly introduced separately as follows:1. The viscoelasticity of polymer solutionThe viscoelasticity of HPAM and xanthan gum(XA) was study by experimental testing in this part, the factors affect on viscoelasticity was analyzed too.Through steady shear flow experiments and dynamic mechanics experiment, the purpose are disclosing difference of viscoelasticity between HPAM and xanthan gum, effect of viscoelasticity rule on various factors.It is shown that first normal force difference and apparent viscosity of HPAM solution increase with the increase of shear rate or molecular weight or concentration or the decrease of salinities, and that the viscoelasticities of XA solutions also increase with the increase of concentrations as HPAM solutions. No obvious difference exists between the energy-storage moduli and the loss moduli of both types of polymer solutions. There was a good linear relation between elastic viscosity/shear viscosity and shear rate. Under seepage flow of oil reservoirs, It can occur a elongation flow of HPAM solutions.2. The pilot test and laboratory test of high-concentration polymer floodingThe results on artificial cores with a Dykstra-Parson Coefficient of 0.72 show that an incremental recovery over water flooding of more than 20% OOIP can be obtained by early time injection of the high molecular weight, high concentration polymer solution, the earlier the better. The incremental recovery is comparable to alkali/surfactant/polymer flooding but at a lower cost.In Daqing Oil Field, a pilot test of high concentration polymer injectivity was conducted on 6 injection wells in August 2002. Three wells are injecting in high permeable pay zones and the other 3 wells in low permeable pay zones. The range of effective permeability (Keff) of the pay zones is 0.354 ~1.06 um2. The results show that high permeable formations (Keff>0.890 um2) are suitable for continuous injection of high concentration polymer solutions (concentration 2,000 ppm ~ 2,500 ppm, molecular weight 17 million Daltons, viscosity 200 ~ 250 mPa.S). In September 2003, the average fluid production of each well was 94.2 tons per day, the average daily oil production of each well was 23.7 tons and average water cut was 74.9%. Compared to low concentration (1,000 ppm) solution flooding, the average fluid production per day of each well remained steady, the daily oil production of each well increased 6.2 tons (an increase of 35.4%) and the average water cut decreased by 6.6%. The results show that the injection of high concentration polymer fluid is very effective and the pilot area will be further expanded.3. The experiments and mechanism of surfactant solution decrease pressure of injection and increase ability of injectionIt is shown that: high-concentration polymer’s inject pressure decrease 47.86%~67.01% after NOS inject into core 1.0 PV; the inject pressure was not up after inject into core 90 PV polymer solution; the lower of NOS interfacial tension(IFT), the lower high-concentration inject pressure.The mechanism of surfactant solution decrease pressure of injection and increase ability of injection are: (1) Get rid of polymer film on the wall of sandstone by inject one of oxidant solution. (2) Surfactant washes out part of residual oil and largen permeability. It is shown that, the amount of moving oil increased, the amount of residual oil decreased, the oil and water’s equal permeability move to right; the area which water and oil are both exist is wider. (3) There is an adsorptive film formed by injecting surfactant on the wall of sandstone, the film is thiner than that of polymer, so it affect little on permeability. Otherwise, the surfactant film can prevent polymer thick film rebuilding, so permeability is not down more.4. The pilot test of decrease high-concentration injecting pressureThe data that six well pilot test shown that: it did decrease high-concentration injecting pressure after the surfactant decreased pressure technic or resin sand fracture technic were employed. The result after using technic above accord with demand that pressure is lower than cracking pressure. It is much better that surfactant decreased pressure if permeability is higher. The period of increasing injection which use surfactant is 2 times more than common fracture. If interlayer is better, and it is necessary that monolayer increase injection, resin sand fracture is predominant, otherwise, the surfactant is better.It is shown that polymer with high-concentration and high- molecular weight solution flooding recovery is 18~24%, and it break through the limit that polymer flooding recovery is 12%. The higher concentration, the higher recovery enhanced. So high-concentration polymer solution can enhance oil recovery further more.更多还原