适用于页岩气开发的高效滑溜水压裂液体系研究

为满足页岩气储层体积压裂对大排量、大液量的要求,需采用滑溜水压裂液体系进行压裂施工。通过大量室内试验,优选出了性能优良的压裂液添加剂,包括减阻剂CY-1、防膨剂CRJ-2和助排剂CPJ-1,并通过浓度优选以及性能评价等试验,建立了一套适合页岩气储层开发的高效滑溜水压裂液体系,具体配方(w)为:0.1%减阻剂CY-1+1.5%防膨剂CRJ-2+0.5%助排剂CPJ-1。对优选的高效滑溜水压裂液体系进行了性能评价,结果表明:该压裂液体系属于假塑性流体,具有良好的流变性能;其降摩阻性能明显优于常规胍胶压裂液体系,具有低摩阻特点;并且压裂液体系对储层段天然岩心的渗透率伤害率仅为5%左右,具有低伤害的特性,能够满足目标区块页岩气储层压裂施工对压裂液性能的要求。     

新型降阻剂DR-12的研制及应用

在页岩气资源的勘探开发中,为改善滑溜水压裂液的性能,通过优选添加剂及低分子聚合物,合成了滑溜水压裂液使用的降阻剂DR-12,对其降阻性能进行了室内评价试验并优化了滑溜水压裂液配方,试验结果表明其降阻性能良好。为了提高DR-12降阻剂的现场施工适应性,优化了施工工艺,主要包括人工裂缝和压裂施工参数的优选,现场试验取得了良好的效果。     

纤维基纳米复合清洁压裂液性能研究

鉴于早期阳离子型清洁压裂液在低渗透砂岩储层现场应用中存在的问题,选取一种阴离子表面活性剂为主剂,制备了纤维基纳米复合清洁压裂液(F-NCF),并对其悬砂、滤失、破胶、岩心伤害及裂缝导流能力的影响等性能进行了评价。结果表明,阴离子型纳米复合清洁压裂液热稳定性明显增强,在70℃、170 s-1条件下,其表观黏度达50 mPa.s;通过纳米TiO2与粘弹性表面活性剂胶束的拟交联作用,提高了F-NCF的降滤失性能,且不影响破胶性能;纤维网状结构有效地改善了F-NCF的静态悬砂性能,且对裂缝导流能力影响较小;同时,该体系对岩心渗透率伤害小,恢复率约为90%,对于提高低渗透油气藏压裂效果具有良好的应用前景。     

EM30降阻剂滑溜水压裂液在水平井中的应用

通过添加了EM30降阻剂的滑溜水压裂液在水平井中进行现场试验,表明滑溜水压裂液在水平井施工中摩阻减阻效果突出,携砂效果显著,无论是射孔液还是压裂液都能反复回收利用,起到了减少储层伤害,缩短施工周期,降低生产成本的作用。     

二叠系致密油储层压裂液体系室内研究

新疆油田准东吉木萨尔县二叠系致密油储层孔隙发育程度差,连通性差,平均孔隙度9.35%、平均渗透率0.0434×10~(-3)μm~2,具有极低渗透性。常规的压裂改造工艺难以满足需求,因此借鉴国内外致密油储层改造工艺方法,在该区采用混合水压裂工艺(滑溜水+胍胶压裂液)体系。本文通过对(滑溜水+胍胶压裂液)体系化学助剂筛选及压裂液性能评价,最终确定了该体系配方,实验结果表明该体系具有耐温耐剪切性好、悬砂性强、低伤害、低摩阻、液体效率高的特性。     

新型VES—SL清洁压裂液研究与应用

常规的瓜胶类水基压裂液由于破胶不彻底,或残渣滞留,造成地层伤害,对支撑剂裂缝导流能力伤害大,特别对于低渗、特低渗储层,严重时增产效果甚微。为降低压裂改造过程中压裂液对油藏和支撑裂缝的伤害,开发研制了VES—SL粘弹性表面活性剂清洁压裂液,对该压裂液的性能进行了研究评价,并在现场进行了几十口井的现场应用,现场应用表明,该压裂液体系具有耐高温（120℃）、携砂能力强,易破胶,易反排,对储层伤害小等特点。     

压裂液返排液对页岩储层裂缝的损害实验评价

页岩气井经过大规模体积压裂施工后会有大量的压裂液返排液滞留在储层裂缝中,这会对页岩储层造成一定的损害。因此,选择涪陵地区某页岩气井压裂液返排液和储层页岩为研究对象,开展了压裂液返排液对页岩储层裂缝的损害实验评价,并分析了其损害机理。结果表明：页岩储层岩心经过压裂液返排液污染后,渗透率明显下降,使用线性胶和滑溜水压裂液返排液污染并烘干后的岩心渗透率损害率分别在31.30%～84.59%和13.97%～61.69%之间,滑溜水压裂液返排液的损害程度稍微弱些。岩心驱替前后压裂液返排液中的固相颗粒粒径分布发生了明显变化,有大量固相颗粒在驱替过程中堵塞在了岩心孔隙和裂缝中。使用线性胶和滑溜水压裂液返排液污染后的页岩导流板导流能力值显著下降,导流板烘干后的导流能力相比初始阶段下降幅度分别为61.48%和31.32%,说明压裂液返排液对页岩储层裂缝造成了严重的损害。建议通过优化压裂液体系性能和建立合理的返排制度来降低压裂液返排液对页岩储层裂缝的损害程度。     

页岩气压裂用滑溜水胶液一体化稠化剂研究

为了提高页岩气现场配液施工效率,降低不同压裂液间配伍性对压裂液性能的影响,利用AM、DMC、DMDB为原料,采用混合胶束水溶液聚合,合成一种滑溜水胶液一体化用稠化剂。用管路摩阻仪和高温流变仪对滑溜水体系降阻性能和组装压裂液体系耐温耐剪切性能进行评价。结果表明,该疏水缔合聚合物溶解时间小于2 min,0. 1%的滑溜水黏度达到10 m Pa·s,降阻率为65. 7%,组装压裂液在90℃,170 s^(-1)条件下剪切2 h,表观黏度大于50 m Pa·s。滑溜水和胶液具有良好的降阻效果及耐温耐剪切性,能够满足滑溜水和压裂液在线混配的要求,可以实现滑溜水胶液一体化。     

全液态缔合压裂液在低渗透水平井的应用

我国新提交储量大多为低渗透难采储量,这类油藏已成为油气开采的潜力,主要采用水平井布井方式开发,受低油价及环保高标准影响,高效经济环保开发已迫在眉睫,而冻胶压裂液成本高,残渣含量大,对低孔低渗透储层伤害较大,影响储层经济有效改造。通过室内优选,研发了由稠化剂及无机盐表活剂组成的全液态缔合压裂液,具有残渣含量少,岩心伤害率低,防膨效果好,携砂性能强等特点,现场应用3口水平井,见到了较好的试验效果,满足了储层低伤害改造需求,且现场配制简单、配液流程大幅简化,价格优势显著,为低渗透储层经济有效改造提供了多功能压裂液体系。     

页岩气压裂用滑溜水胶液一体化稠化剂研究

为了提高页岩气现场配液施工效率,降低不同压裂液间配伍性对压裂液性能的影响,利用AM、DMC、DMDB为原料,采用混合胶束水溶液聚合,合成一种滑溜水胶液一体化用稠化剂。用管路摩阻仪和高温流变仪对滑溜水体系降阻性能和组装压裂液体系耐温耐剪切性能进行评价。结果表明,该疏水缔合聚合物溶解时间小于2 min,0. 1%的滑溜水黏度达到10 m Pa·s,降阻率为65. 7%,组装压裂液在90℃,170 s~(-1)条件下剪切2 h,表观黏度大于50 m Pa·s。滑溜水和胶液具有良好的降阻效果及耐温耐剪切性,能够满足滑溜水和压裂液在线混配的要求,可以实现滑溜水胶液一体化。     

Synthesis and performance evaluation of a new drag reducer based on acrylamide/12-allyloxydodecyl acid sodium

Hydraulic fracturing with slickwater is a field-proven stimulation technology used in tight reservoirs. Because of the high pumping rate associated with slickwater fracturing, drag reduction (DR) is critical in minimizing pressure drop and the success of oilfield operations. In this paper, a new type of drag reducer (SPR) was synthesized with acrylamide and 12-allyloxydodecyl acid sodium, and its drag reduction performance was evaluated. The results showed that the new drag reducer features low molecular weight, fast-dissolving rate and low interfacial tension. The algorithm of estimating the drag reduction rate of non-Newtonian fluid SPR was proposed and validated. Empirical or semianalytical models for estimating the friction ratio (σ) or friction factor (λ or f) were used to simulate the turbulence behavior of the SPR drag reducer under different Reynolds numbers (Re). The modified Virk's correlation could accurately model the turbulent behavior of the SPR drag reducer. A unified calculation formula was established in this study for different pipe diameters.     

A new model for simulating particle transport in a low‐viscosity fluid for fluid‐driven fracturing

Fluid‐driven fracture (i.e., Hydraulic fracturing) is an important way to stimulate the well productivity in the development of unconventional reservoirs. A low‐viscosity fluid called slickwater is widely used in the unconventional fracturing. It is a big challenge to simulate the particle (or proppant) transport in the low‐viscosity fluid in a field‐scale fracture. A new model to simulate particle transport in the low‐viscosity fluid in a field‐scale fracture is developed. First, a new parameter is defined, called the rate of proppant bed wash‐out, by which we incorporated the mechanism of proppant bed wash‐out into Eulerian‐Eulerian proppant transport model. Second, we proposed a novel way to consider the effect of proppant settling on the proppant concentration in the upper layer (or suspending layer) to accurately simulate the proppant transport. Additionally, a dimension reduction strategy was used to make the model quickly solved. Our simulation results were compared with published experimental data and they were consistent. After validation, the effect of fluid viscosity, injection rate, fracture height, and proppant concentration on the proppant distribution in a fracture is investigated. This study provides a new model to simulate particle transport. Meanwhile, it gives critical insights into understanding particle transport in the field‐scale fracture. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3542–3552, 2018     

A review of fracturing fluid systems used for hydraulic fracturing of oil and gas wells

Hydraulic fracturing has been used by the oil and gas industry as a way to boost hydrocarbon production since 1947. Recent advances in fracturing technologies, such as multistage fracturing in horizontal wells, are responsible for the latest hydrocarbon production boom in the US. Linear or crosslinked guars are the most commonly used fluids in traditional fracturing operations. The main functions of these fluids are to open/propagate the fractures and transport proppants into the fractures. Proppants are usually applied to form a thin layer between fracture faces to prop the fractures open at the end of the fracturing process. Chemical breakers are used to break the polymers at the end of the fracturing process so as to provide highly conductive fractures. Concerns over fracture conductivity damage by viscous fluids in ultra‐tight formations found in unconventional reservoirs prompted the industry to develop an alternative fracturing fluid called “slickwater”. It consists mainly of water with a very low concentration of linear polymer. The low concentration polymer serves primarily to reduce the friction loss along the flow lines. Proppant‐carrying capability of this type of fluids is still a subject of debate among industry experts. Constraints on local water availability and the potential for damage to formations have led the industry to develop other types of fracturing fluids such as viscoelastic surfactants and energized fluids. This article reviews both the traditional viscous fluids used in conventional hydraulic fracturing operations as well as the new family of fluids being developed for both traditional and unconventional reservoirs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40735.     

Synthesis and application of nonionic polyacrylamide with controlled molecular weight for fracturing in low permeability oil reservoirs

Nonionic polyacrylamide (NPAM) with controlled molecular weight was successfully synthesized as a gel fracturing fluid by aqueous solution polymerization. The effects of the monomer concentration, initiator concentration, reaction time, feeding temperature and reaction temperature on the molecular weight were systematically investigated through single‐factor and orthogonal experiments. The NPAM molecular weight can be controlled by adjusting these factors. The decisive factor is the acrylamide concentration, whereas the initiator concentration and feeding temperature are secondary factors. These synthetic NPAMs can be crosslinked with zirconium acetate to produce a gel fracturing fluid for use in low permeability oil reservoirs. Gel fracturing fluids based on synthetic NPAMs have high shear resistance, low filtration performance, easy gel breaking performance, good proppant carrying capability and low core damage capability. By adjusting the NPAM or crosslinker concentrations, the gel fracturing fluid can be adapted for use in low permeability oil reservoirs for a wide temperature range (60–120°C). © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41637.     

一种适合松南深层储层的缔合型压裂液

针对松南地区深层储层埋藏深、岩性致密、微裂缝发育、渗透率低、地层温度高、破裂压力高等特点,采用新型缔合型稠化剂研制了一种新型低伤害压裂液.试验表明该压裂液抗温性能良好,残渣含量小于10mg/L,储层岩芯伤害率小于15％,支撑裂缝导流能力保留率大于10％,降阻率大于70％.现场应用取得了良好效果,为松南地区深层储层的开发提供了一条新的途径.     

煤层气压裂液伤害对比实验研究

我国煤层气储层条件较差,具有低渗、低孔、非均质性强的特点,均存在的问题就是一般开采方式效果不好。压裂是煤层岩增产的主要技术之一,而压裂的关键在于压裂液体系的选择,压裂液对储层的伤害将会导致达不到理想的产量。通过室内实验研究,进行煤层气压裂伤害评价实验,对压裂液体系的进行优选,选择浓度低,低摩阻的清洁压裂液,提高煤层气单井产量,改善井底渗流条件,提高煤层气渗透率以及储层渗透能力。解决宁武地区煤层气井压裂改造成功率低的问题,取得了巨大的突破,增产效果明显。     

一种经济型清洁压裂液配方研究与性能评价

粘弹性表面活性剂(Viscoelastic surfactant,下文简称VES)压裂液与传统聚合物压裂液不同,可消除残余聚合物对支撑剂充填层的堵塞,并能有效提高导流能力,减少对地层的损害及污染,压后油气产量比使用传统压裂液有显著提高。介绍了VES压裂液的原理及配方设计原则。通过室内试验确定了一种经济型VES压裂液的配方,并对其性能进行了相关评价。     

支撑剂回流理论研究

压裂是低渗透油藏的重要开发手段,而压裂返排施工关乎压裂成败。通过对压裂过程中的支撑剂进行受力分析,利用牛顿第二定律分析了支撑剂在水平和竖直方向上的运动状态,建立了支撑剂回流模型。利用室内模拟实验,模拟了在单条裂缝中的支撑剂运动,分析了不同返排流量下的支撑剂运动状态,验证了支撑剂回流模型的准确性。通过室内模拟实验和回流模型计算分析了实际压裂过程中支撑剂在裂缝中的运动,得到支撑剂在裂缝中的运动距离相对于裂缝半长很小,为现场施工过程中进行顶替返排提供理论支撑。     

稠化水清洁压裂液在陇东油田的应用

压裂是低渗油藏改造的主要措施之一,压裂液性能是影响施工后增产效果的一个重要因素。目前陇东油田应用的压裂液主要为水基羟甲基胍胶压裂液,该压裂液存在破胶后有残渣（达3%～10%）、容易腐败、返排率低的缺点,对储层有较大的伤害（伤害率达18%以上）。稠化水清洁压裂液是表面活性剂、酸液和清水按比例混合后达到携砂压裂要求的新型压裂液体系,可以有效降低压裂液对储层的伤害,该体系在三叠系油井试验取得成功后,进一步优化配方,在侏罗系油井推广试验,取得了较好的效果,为低渗、特低渗油藏的改造增加一个新的增产途径。     

低温煤层气清洁压裂液破胶性能评价及现场应用

清洁压裂液不仅具有较强的携砂能力,同时具有较强的造缝能力(滤失系数小),且摩阻低等优点。然而浅层煤层气温度较低(25?35℃)。煤层气储层内缺乏能使清洁压裂液破胶的液态烃或游离状态的自由水,这使得清洁的压裂液不易破裂,在压裂过程中会造成严重的储层破坏。主要针对低温煤层气清洁压裂液体系破胶剂及破胶性能进行了探讨,开发出适用于低温煤层气清洁压裂液体系的破胶剂,该破胶剂可以在25℃低温下彻底破胶清洁压裂液,同时对压裂液造成的破坏程度进行评估。压裂液破坏率仅为11%。清洁压裂液系统已在山西省沁水盆地应用。