Preparation and performance evaluation of the slickwater using novel polymeric drag reducing agent with high temperature and shear resistance ability

Slickwater fracturing fluids are widely used in the development of unconventional oil and gas resources due to the advantages of low cost,low formation damage and high drag reduction performance.However,their performance is severely affected at high temperatures.Drag reducing agent is the key to determine the drag reducing performance of slickwater.In this work,in order to further improve the temperature resistance of slickwater,a temperature-resistant polymeric drag reducing agent(PDRA)was synthesized and used as the basis for preparing the temperature-resistant slickwater.The slickwater system was prepared with the compositions of 0.2 wt%PDRA,0.05 wt%drainage aid nonylphenol polyoxyethylene ether phosphate(NPEP)and 0.5 wt%anti-expansion agent polyepichlorohydrindimethylamine(PDM).The drag reduction ability,rheology properties,temperature and shear resistance ability,and core damage property of slickwater were systematically studied and evaluated.In contrast to on-site drag reducing agent(DRA)and HPAM,the temperature-resistant slickwater demonstrates enhanced drag reduction efficacy at 90℃,exhibiting superior temperature and shear resistance ability.Notably,the drag reduction retention rate for the slickwater achieved an impressive 90.52%after a 30-min shearing period.Additionally,the core damage is only 5.53%.We expect that this study can broaden the application of slickwater in high-temperature reservoirs and provide a theoretical basis for field applications.

A novel model for the proppant equilibrium height in hydraulic fractures for slickwater treatments

The proppant equilibrium height is the basis of investigating proppant distributions in artificial fractures and has a great significant influence on hydraulic fracturing effect.There are two shortcomings of current research on proppant equilibrium heights,one of which is that the effect of fracture widths is neglected when calculating the settling velocity and another of which is that the settling bed height is a constant when building the settling bed height growth rate model.To fill those two shortcomings,this work provides a novel model for the proppant equilibrium height in hydraulic fractures for slickwater treatments.A comparison between the results obtained from the novel model and the published model and experimental results indicates that the proposed model is verified.From the sensitivity analysis,it is concluded that the proppant equilibrium height increases with an increasing proppant density.The proppant equilibrium height decreases with an increase in the slickwater injection rate and increases with an increase in the proppant injection rate.The increase in proppant diameter results in an increasing the friction factor,which makes proppant equilibrium heights decrease.Meanwhile,the increase in proppant sizes results in an increase in proppant settling rates,which makes the proppant equilibrium height increase.When the effect of the proppant diameter on settling rates is more significant than that on friction factors,the equilibrium height increases with an increasing proppant size.This work provides a research basis of proppant distributions during the hydraulic fracture.

生物柴油基减阻剂研制及滑溜水压裂液体系构建

为了解决常规白油基滑溜水体系在运输过程中容易分层以及减阻剂溶解太慢、对环境污染大等问题,首先通过测试不同相对分子质量及水解度的减阻剂F1~F6的溶解性和增黏性能优选了减阻剂F4;通过对稠化剂、分散剂及固液比筛选,研制了配方为34.0%生物柴油+3.0%稠化剂F-120+3.0%分散剂S-85+60.0%减阻剂F4的生物柴油基悬浮减阻剂,并将生物柴油基悬浮减阻剂与助排剂、防膨剂构建变黏滑溜水压裂液体系。实验结果表明,减阻剂F4在180℃下恒温剪切2 h后的表观黏度保留率为33.0%,热稳定性较好;变黏滑溜水压裂液具有良好的抗剪切能力和抗温性能,在剪切速率为170 s^(-1)下长期剪切后,常温下黏度保留率均可达90%以上,90℃下黏度保留率均达50%以上,其中高黏滑溜水压裂液黏度保留率可高达70%以上,低黏滑溜水压裂液的减阻率可达70%以上;高黏滑溜水压裂液的携砂性能比低、中黏滑溜水压裂液的高,且沉降速率最低,为0.005272 m/min。变黏滑溜水压裂液破胶后表面张力均小于27 m N/m,与煤油间的界面张力均小于2.0 mN/m,破胶液黏度均小于5.0mPa·s,且残渣含量均小于50 mg/L,满足标准要求。

延长油田东部浅层致密油储层驱油压裂技术及应用

南泥湾采油厂浅层致密油储层采用滑溜水分段压裂取得初步成效,但产量递减快,原因之一就是油藏能量不足。针对浅层致密油藏增能需求,采用大排量、大液量、低砂比的驱油型滑溜水压裂液滞留地层,补充地层能量,通过焖井进行油水置换,形成驱油压裂技术。根据施工排量控制总射孔数,按照每孔排量最少0.3 m^(3)/min进行压裂,压后焖井,通过优化压裂缝模拟设计形成较大的储层改造体积,达到体积压裂的效果。评132井区平2井现场试验结果表明,该工艺实施简单,整个施工泵压较低且平稳,排量稳定,取得了较好的增产效果。

滑溜水压裂液用超疏水型多功能减阻剂制备及应用

目前常规滑溜水压裂液体系普遍具有减阻、携砂、抗盐和耐温等多种功能,但均没有考虑通过改变储层表面润湿性而实现储层保护功能。因此,以丙烯酸、丙烯酰胺、自制材料2-丙烯酰胺基-2-苯基乙烷磺酸和疏水改性剂等为原料,合成了一种超疏水型多功能压裂液用减阻剂SHJZ-1。通过红外光谱仪对合成产物减阻剂结构进行表征,且通过高温高压岩心动态损害评价系统、接触角测量仪、哈克流变仪、闭合管路摩阻测试仪等方法对其性能进行综合评价。结果表明,该减阻剂SHJZ-1溶解时间短,起黏快;当盐水的矿化度达到40000 mg/L时,0.5%SHJZ-1溶液的减阻率在68%左右;0.15%SHJZ-1溶液在140℃下高温老化,减阻率仍能达到70%以上;1.3%SHJZ-1溶液处理后的岩心表现出超疏水效果,岩心接触角为151.21°;该减阻剂溶液对岩心平均渗透率伤害率仅为11.6%。超疏水型多功能压裂液体系在HX-1井顺利进行了现场应用,压裂过程中压裂液性能比较平稳,压后产量与临井相比提升10%以上,实现了提质增效的目的。

Experimental study on proppant-carrying migration and settlement of slickwater in narrow plate fractures based on PIV/PTV

Hydraulic fracturing is the primary method used for oilfield stimulation,and the migration and settlement pattern of proppant plays a crucial role in the formation of high conductivity propping fractures in the reservoir.This study summarizes two growth modes of sand dune:the‘overall longitudinal growth’mode and the‘push growth along fracture length direction’mode.To investigate these modes,a twophase velocity test is conducted using PIV,and the exposure difference is utilized to separate the tracer and track the single-phase velocity.By analyzing the slickwater flow field and proppant velocity field,the micro-motion mechanism behind the two dune growth modes is quantitatively examined.The results indicate that mode 1 growth of the sand dune occurs when a pump with a large mesh number,high polymer viscosity,and large displacement is used.On the other hand,mode 2 growth is observed when a pump with a small mesh number,low polymer viscosity,and small displacement is employed.It is important to note that there is no clear boundary for the migration and sedimentation mode of proppant,as they can transition into each other under certain conditions.These modes only exist during specific stages of sand dune growth.In the case of the‘backflow’pattern,the settlement of proppant is primarily influenced by the vortex structure of slickwater.Conversely,in the‘direct’pattern,the proppant is propelled forward by the drag of the fluid and settles due to its own gravity.Once the proppant placement reaches equilibrium,the direction of proppant velocity follows a normal distribution within 0°.This approach establishes a connection between the overall placement of the sand dune and the microscopic movement of the proppant and slickwater.Optimizing construction parameters during fracturing construction can enhance the effectiveness of distal proppant placement in fractures.

The effects of various factors on spontaneous imbibition in tight oil reservoirs

Slickwater fracturing fluids have gained widespread application in the development of tight oil reservoirs. After the fracturing process, the active components present in slickwater can directly induce spontaneous imbibition within the reservoir. Several variables influence the eventual recovery rate within this procedure, including slickwater composition, formation temperature, degree of reservoir fracture development, and the reservoir characteristics. Nonetheless, the underlying mechanisms governing these influences remain relatively understudied. In this investigation, using the Chang-7 block of the Changqing Oilfield as the study site, we employ EM-30 slickwater fracturing fluid to explore the effects of the drag-reducing agent concentration, imbibition temperature, core permeability, and core fracture development on spontaneous imbibition. An elevated drag-reducing agent concentration is observed to diminish the degree of medium and small pore utilization. Furthermore, higher temperatures and an augmented permeability enhance the fluid flow properties, thereby contributing to an increased utilization rate across all pore sizes. Reduced fracture development results in a lower fluid utilization across diverse pore types. This study deepens our understanding of the pivotal factors affecting spontaneous imbibition in tight reservoirs following fracturing. The findings act as theoretical, technical, and scientific foundations for optimizing fracturing strategies in tight oil reservoir transformations.

Research on the Performance of New Weighted Slippery Water Fracturing Fluid System

Deep and ultra-deep reservoirs have dense matrix and high fracture pressure, which leads to high pressure and difficulty in fracturing construction. Conventional aggravated fracturing fluids have the problems of low aggravation efficiency, high friction resistance, etc., and the reduction of construction pressure cannot reach the theoretical effect. In view of the above problems, this paper adopts the weighting agent HD160 and the drag reducing agent JHFR-2 to form a new type of weighted slippery water fracturing fluid system. And the weighting performance, drag reduction performance, corrosion performance, anti-expansion performance and reservoir damage of this system were studied. The results show that the density of the system is adjustable within 1.1 - 1.6 g·cm−3, and the drag reduction rate can be up to 68% at 1.5 g·cm−3, with low corrosion rate, surface tension less than 28 mN·m−1, anti-expansion rate as high as 94.5%, and the damage rate of the reservoir permeability is less than 10%, which is of good application prospect.

页岩油压裂用纳米变黏滑溜水的合成及其性能评价

常规滑溜水压裂液已经成功运用于页岩等非常规油气储层压裂中,但其携砂性能差、渗吸采收率低的问题仍然未得到有效解决。针对这一问题,合成一种新型纳米变黏滑溜水,该体系不仅具有常规滑溜水优异的减阻特性,还兼具了较强的变黏携砂性能。另外,该体系含有优选的纳米乳液,可将混合润湿或油润湿的页岩油储层改性为水润湿,具有强渗吸置换作用。通过一系列室内实验评价可以发现:碳纳米渗吸(carbon nano imbibition,CNI)体系纳米变黏滑溜水为乳液状,可实时在线配制,通过调整其浓度,黏度发生显著变化,达到低浓度时高减阻、高浓度时强携砂的效果,残渣含量及对储层伤害低,实现了一剂多效,同时它还具有常规滑溜水与瓜胶携砂液所没有的改性驱油的效果,从而提高原油采收率。纳米变黏滑溜水同时具备高减阻、高携砂、低伤害和强置换的性能,可作为未来页岩油压裂的主体压裂液。

深层页岩气储层耐温抗盐型滑溜水压裂液体系研究

为满足深层页岩气储层压裂施工对压裂液性能的要求,以丙烯酰胺、刚性基团阳离子单体和N-乙烯吡咯烷酮为原料复配了一种高效耐温抗盐型降阻剂GHR-1,并结合助排剂和黏土稳定剂,形成了一套适合深层页岩气储层的耐温抗盐型滑溜水压裂液体系,对其综合性能进行了评价。结果表明:滑溜水体系的防膨性能、表面张力、pH值、运动黏度、残渣含量以及与地层水的配伍性等基本指标均满足行业标准要求。体系的耐温抗盐性能较好,在最高温度为140℃或者矿化度达到204.8 g/L时,滑溜水的减阻率仍能达到70%以上。体系对目标区块页岩储层岩心的基质渗透率伤害率低于10%,具有较好的储层保护效果。耐温抗盐型滑溜水压裂液体系在NX-1井成功进行了现场应用,施工过程中滑溜水压裂液性能比较稳定,现场减阻效果较好,测试产气量达到了42.35×10^(4)m^(3)/d,压裂增产效果较好。

组合粒径+滑溜水携砂铺置规律及导流能力——以吉木萨尔页岩油储层为例

为了解决页岩油组合粒径+滑溜水的支撑剂加砂工艺中裂缝有效支撑差、导流能力弱的问题,建立支撑剂粒径分布的稠密离散相模型(DDPM),研究压裂主缝中组合粒径支撑剂加砂运移及铺置规律,并基于运移规律模拟结果,开展劈裂页岩岩板组合粒径不同铺置模式下的室内导流能力评价。结果表明:滑溜水携砂液体系下,裂缝内支撑剂叠置铺置时,后注入的支撑剂叠置于先注入支撑剂的顶端,且先注入的支撑剂会被后续注入的支撑剂向远端推移一定距离;组合粒径中粒径配比差异对于支撑剂运移形成的砂堤形态影响较小;大粒径组合逐级注入的方式更利于支撑剂在近缝口和裂缝内垂向铺置;在低闭合压力(p≤40 MPa)、铺砂浓度5 kg/m^(2)条件下,沉降铺置方式最利于提高裂缝导流能力,其次为混合铺置,分段铺置方式最差;高闭合压力下(p>40 MPa),铺置方式对裂缝导流能力影响较弱。综合支撑剂运移模拟和导流能力评价结果,建议吉木萨尔页岩油组合粒径加砂工艺采用逐级注入的方式,并保证组合粒径中大粒径拥有较大配比。

耐高矿化度超支化聚合物滑溜水压裂液减阻与流变性关系研究

滑溜水压裂液是页岩气等非常规油气藏开采的重要材料,为明确高矿化度下聚合物滑溜水压裂液流变性与减阻性能关系,研究了超支化聚合物在不同浓度和不同矿化度下的流变性能,同时在大型摩擦阻力测试装置中测试其压差数据和摩擦阻力性能,在20万矿化度下减阻率可以达到70%左右。分析了聚合物的浓度、高矿化度对超支化聚合物流变性与减阻率的影响。并将计算得到的超支化聚合物在管路中流动的摩擦阻力系数(f)、广义雷诺数(Re)与聚合物溶液流变学参数(n)相关联,建立了表征高矿化度条件下超支化聚合物溶液摩擦阻力系数新方程,并获得了高矿化度下滑溜水摩阻系数与Re的幂律关系式。

新疆油田玛湖砂岩储层自悬浮支撑剂现场试验

目前大排量滑溜水压裂工艺已成为非常规油气资源开发的主要手段,由于滑溜水携砂能力有限,支撑剂在裂缝中沉降速度快、运移距离短,储层改造效果有待进一步提升。自悬浮支撑剂表面包裹的水溶性材料可提升其在滑溜水或清水中的悬浮效果,增大裂缝支撑体积。实验结果表明,自悬浮支撑剂基本技术指标满足标准要求,20%砂比时在自来水中全悬浮时间小于40 s,且在90℃条件下能够稳定悬浮2 h以上,混合液破胶彻底。新疆油田在玛湖砂岩储层开展现场试验,实现清水连续携砂,最高砂质量浓度480 kg/m^(3),施工压力平稳。自悬浮支撑剂清水压裂技术在新疆油田的成功应用为后期油气资源工艺技术的选择提供参考。

可降解微交联减阻剂的开发及应用

针对常规线型减阻剂配制中高黏滑溜水时增黏能力弱、使用量偏高的问题,在线型减阻剂分子结构中引入了含丙烯酸酯键的交联结构,开发了可降解微交联减阻剂。实验结果表明,该微交联减阻剂能在30~40 s溶解,减阻率可达70%以上;微交联减阻剂增黏能力较线型减阻剂更强,但添加量超过0.4%(w)后,滑溜水黏度增加趋势变缓;黏度要求10~30 mPa·s时,微交联减阻剂比线型减阻剂的加量(w)下降20%~30%;相比线型减阻剂,微交联减阻剂配制的滑溜水有更高的屈服强度、更长的松弛时间以及更高的弹性模量与黏性模量比值,表明微交联减阻剂配制的滑溜水中弹性特征占比更高;微交联减阻剂配制的滑溜水动态支撑剂运移距离更远、铺砂剖面更好;微交联减阻剂在地层水中能够发生降解,90℃下48 h后滑溜水黏度下降率超过80%;微交联减阻剂现场应用效果良好,相比常规减阻剂用量下降20%以上。

一种适用于页岩油气井工厂化体积压裂的新型液体破胶剂

针对页岩油气井工厂化体积压裂过程中固体粉末破胶剂使用存在人工强度大、安全风险高、且易出现混配不均匀导致破胶效果差的问题,基于过硫酸盐氧化破胶机理,研制了一种新型液体破胶剂。通过室内实验分析了配方组成、存储方式、存储时间、pH值等因素对液体破胶剂性能的影响。结果表明:密闭保存环境下过硫酸钾液体破胶剂性能更稳定,同时,体积浓度为0.06%或0.05%、温度90℃、破胶时间4 h的条件下该液体破胶剂分别对冻胶压裂液体系和变黏滑溜水两种常用压裂液体系均能彻底破胶,破胶液黏度小于5 mPa·s,满足现场压裂液破胶技术要求。历时23 d,在大庆油田1口页岩油水平井43段体积压裂成功应用,放喷求产阶段返排液黏度均小于2 mPa·s,破胶性能好、破胶彻底,有效解决了固体粉末破胶剂使用过程中存在的难题,为工厂化体积压裂施工提供了技术支撑。

反相乳液型减阻剂及滑溜水体系的研发与应用

由于常规压裂液降阻效果差,对储层伤害大,为了大幅度降低施工摩阻,降低施工压力,改善压裂改造效果,采用反相乳液聚合法合成了一种用于压裂的反相乳液型减阻剂,并以其为主剂,与优选出的配伍性能好、协同效应好的黏土稳定剂、助排剂等复配形成了一种新型滑溜水体系。室内试验表明：0.10%~0.15%反相乳液型减阻剂溶液的减阻率达到65%以上;新型滑溜水体系的减阻率达到65%,且具有较高的防膨胀和助排性能,较好的耐温抗盐性能。新型滑溜水体系已在青海、江汉、华北等油田薄互致密储层压裂和页岩油气井分段压裂中进行了应用,表现出了良好的特性,获得了良好的改造效果。该体系能够满足页岩油气储层及致密储层压裂的需要,且能降低大型压裂的施工成本。

页岩气藏清水压裂悬砂效果提升实验

针对页岩气藏压裂中清水压裂悬砂效果较差问题,分析压裂液和支撑剂性质,通过实验提出增强清水压裂悬砂效果方法:纤维复合清水压裂液技术和超低密度支撑剂技术.结果表明:纤维的加入不仅使清水压裂液的悬砂性能得到提高,同时还可以显著降低液体摩阻.低密度支撑剂可以降低沉降速度50%以上.综合采用纤维复合清水压裂液技术和超低密度支撑剂技术,支撑剂2h的沉降率为17%.不仅可以提高清水压裂的开发效果,还可以降低对地面泵车排量的要求,对于页岩气藏的开发具有指导意义.

水溶性减阻剂在页岩气滑溜水压裂中的应用进展

滑溜水压裂是致密页岩气开采主要采用的增产手段,水溶性减阻剂是滑溜水压裂液中用于降低流体在管道输送过程中所受阻力的化学试剂。介绍了减阻剂的减阻机理,综述了水溶性减阻剂在页岩气滑溜水压裂领域应用的研究进展,包括生物基多糖减阻剂、聚氧化乙烯减阻剂和聚丙烯酰胺类减阻剂在页岩气压裂领域应用的研究现状。对水溶性减阻剂的应用前景进行了展望,减阻性能好、对储层伤害低、环境友好和成本较低廉的减阻剂是未来研究的重点。

川中沙溪庙致密油藏压裂液技术研究及应用

川中沙溪庙致密油藏为特低孔、低渗致密储层,压裂工艺要求先以滑溜水大排量泵注方式在地层中形成复杂缝网,再以冻胶压裂液造主缝,形成大规模的连通性体积缝网。将聚丙烯酰胺类滑溜水与低分子量胍胶类冻胶压裂液复合应用,开发出了适合川中沙溪庙储层的'滑溜水+冻胶'混合压裂液技术。其中,滑溜水具有低摩阻、高效防膨等特点;冻胶压裂液具有耐剪切、低伤害等特点;混合压裂液体系的破乳效果好、返排能力强。现场试验表明:'滑溜水+冻胶'混合压裂液技术具有良好的储层改造效果,在G36井、G117井应用获得成功,现场降阻率达61.5%~64.8%、返排率】40%,返排液油水界面清晰,获井口测试产油45.1t/d。

大规模增产作业中液体的回用技术探讨

针对页岩气、致密气等非常规气藏体积压裂过程中存在的配液用水缺乏、压裂返排液处理困难、环境污染风险大等问题,探讨了大规模增产作业中的液体回用技术。大规模增产作业对水资源的需求量大,井场用水供需矛盾突出,且产生的压裂返排液量大,面临的环境形势严峻,制约了非常规气藏的开发。压裂返排液的组成复杂,其成分主要取决于压裂液配液水质、压裂液化学组成、储层地质化学、地层水等,影响其回用时的压裂液性能,需针对性地进行处理。大规模增产作业中的液体回用技术主要是通过杀菌、沉降除机械杂质、化学沉淀除高价金属离子、补充损失的添加剂等措施使压裂返排液的性能满足再次施工要求。该技术在四川盆地须家河致密气储层及侏罗系致密油储层中得到了广泛应用,返排液回收后的利用率达95%,节约了水资源,实现了循环经济。