Cause analysis and solutions of water blocking damage in cracked/non-cracked tight sandstone gas reservoirs

After hydraulic fracturing treatment,a reduction in permeability caused by the invasion of fracturing fluids is an inevitable problem,which is called water blocking damage.Therefore,it is important to mitigate and eliminate water blocking damage to improve the flow capacities of formation fluids and flowback rates of the fracturing fluid.However,the steady-state core flow method cannot quickly and accurately evaluate the effects of chemical agents in enhancing the fluid flow capacities in tight reservoirs.This paper introduces a time-saving and accurate method,pressure transmission test(PTT),which can quickly and quantitatively evaluate the liquid flow capacities and gas-drive flowback rates of a new nanoemulsion.Furthermore,scanning electron microscopy(SEM)was used to analyze the damage mechanism of different fluids and the adsorption of chemical agents on the rock surface.Parallel core flow experiments were used to evaluate the effects of the nanoemulsion on enhancing flowback rates in heterogeneous tight reservoirs.Experimental results show that the water blocking damage mechanisms differ in matrices and fractures.The main channels for gas channeling are fractures in cracked cores and pores in non-cracked cores.Cracked cores suffer less damage from water blocking than non-cracked cores,but have a lower potential to reduce water saturation.The PTT and SEM results show that the permeability reduction in tight sandstones caused by invasion of external fluids can be list as guar gum fracturing fluid>slickwater>brine.Parallel core flow experiments show that for low-permeability heterogenous s andstone reservoirs with a certain permeability ratio,the nanoemulsion can not only reduce reverse gas channeling degree,but also increase the flowback rate of the fracturing fluid.The nanoemulsion system provides a new solution to mitigate and eliminate water blocking damage caused by fracturing fluids in tight sandstone gas reservoirs.

Water blocking effect caused by the use of hydraulic methods for permeability enhancement in coal seams and methods for its removal

To research techniques for removing the water blocking effect caused by hydraulic applications in coal seams,the use of surfactants is proposed,based on the mechanics of the water blocking effect.Centrifugal experiments were used to validate the effects of using surfactants;the results show that after dealing with vacuum saturation with water,the volume of micropores decreases,which results in a larger average pore size,and the volume of transitional pores,mesopores,macropores and total pores increases.Based on the distribution of pore size,the operation mode of ‘‘water infusion after gas extraction,then continuing gas extraction" is recommended to improve the volume of coal mine gas drainage.When the reflectance of vitrinite in coal samples is less than 1,using the surfactants Fast T,1631,APG,BS can mitigate the damage caused by the water blocking effect.But when the reflectance of vitrinite is larger than 1.4,the damage caused by the water blocking effect can be increased.When the surfactant CMC is used in hydraulic applications,the capillary forces of coal samples are almost negative,which means the capillary force is in the same direction as the gas extraction.The direction of capillary forces benefits the gas flow.So,using CMC can play an active role in removing the water blocking effect.Centrifugal experiments confirm that using CMC can effectively remove the water blocking effect,which has a beneficial effect on improving the gas drainage volume.

Technology of reinforcement maintenance and blocking against water for large section chamber

The scheme and construction measurement of reinforcement and blocking against water for winder chamber after destroyed by mining influence have been introduced in this paper. The basic principle and advantages of bolting and grouting lining have been also listed. Bolting and grouting lining can increase the integrity and load-carrying capacity of supporting framework and it can assure the stability of supporting framework. It possesses not only the flexible and yielding capacity of bolting and shotcrete lining, but also the effect of rigid support such as metal support and brickwork, forming many kinds of support system, maintaining the stability of roadway together.

Effects of Irrigation Water Quality and Drip Tape Arrangement on Soil Salinity,Soil Moisture Distribution,and Cotton Yield (Gossypium hirsutum L.) Under Mulched Drip Irrigation in Xinjiang,China

More and more attention is being focused on saline water utilization in irrigation due to the shortage of fresh water to agriculture in many regions. For purpose of reducing the risks of using of saline water for irrigation, the mechanism of soil moisture and salinity distribution and transport should be well understood for developing optimum management strategies. In this paper, field experiments were carried out at Junggar Basin, China, to study the effects of drip irrigation water quality and drip tape arrangement on distribution of soil salinity and soil moisture. Six treatments were designed, including two drip tape arrangement modes and three irrigation water concentration levels （0.24, 4.68, and 7.42 dS m^-l）. Results showed that, soil moisture content （SMC） directly beneath the drip tape in all treatments kept a relatively high value about 18% before boll opening stage; the SMC in the narrow strip in single tape arrangement （Ms） plot was obviously lower than that in the double tapes arrangement （Md） plot, indicating that less sufficient water was supplied under the same condition of irrigation depth, but there was no significant reduction in yield. Mulching had not significant influence on salt accumulation but the drip tape arrangement, under the same condition of irrigation water depth and quality, compared with Md, Ms reduced salt accumulation in root zone and brought about relatively high cotton yield.

Pore network modeling of water block in low permeability reservoirs

A pore network model was used in this paper to investigate the factors, in particular, throat radius, wettability and initial water saturation, causing water block in low permeability reservoirs. A new term - ＇relative permeability number＇ （RPN） was firstly defined, and then used to describe the degree of water block. Imbibition process simulations show that the RPN drops in accordance with the extension of the averaged pore throat radius from 0.05 to 1.5 μm, and yet once beyond that point of 1.5 μm, the RPN reaches a higher value, indicating the existence of a critical pore throat radius where water block is the maximum. When the wettability of the samples changes from water-wet to weakly water-wet, weakly gas-wet, or gas（oil）-wet, the gas RPN increases consistently, but this consistency is disturbed by the RPN dropping for weakly water-wet samples for water saturations less than 0.4, which means weakly waterwet media are more easily water blocked than water-wet systems. In the situation where the initial water saturation exceeds 0.05, water block escalates along with an increase in initial water saturation.

Mechanisms of shale hydration and water block removal

Shale samples of Silurian Longmaxi Formation in the Changning area of the Sichuan Basin, SW China, were selected to carry out scanning electron microscopy, CT imaging, high-pressure mercury injection, low-temperature nitrogen adsorption and imbibition experiments to compare the hydration characteristics of montmorillonite and illite, analyze the main factors affecting the water block removal of shale, and reveal the mechanisms of pore structure evolution during shale hydration. The hydration characteristics of shale are closely related to the composition of clay minerals, the shale with high illite content is not susceptible to hydration and thus has limited room for pore structure improvement;the shale with high montmorillonite is susceptible to hydration expansion and thus has higher potential of pore structure improvement by stimulation;the shale with high illite content has stronger imbibition in the initial stage, but insufficient diffusion ability, and thus is likely to have water block;the shale with high montmorillonite content has weaker imbibition in the initial stage but better water diffusion, so water blocking in this kind of shale can be removed to some degree;the shale reservoir has an optimal hydration time, when it is best in physical properties, but hydration time too long would cause damage to the reservoir, and the shale with high illite content has a shorter optimal hydration time;inorganic cations can inhibit the hydration of clay minerals and have stronger inhibition to illite expansion, especially K^(+);for the reservoir with high content of montmorillonite, the cation content of fracturing fluid can be lowered to promote the shale hydration;fracturing fluid with high K^(+) content can be injected into reservoirs with high illite content to suppress hydration.

Research on Hydraulic Block Scenarios in the Land Conservation Zone of the Headwaters Area of Jinshu Bay

[Objective] The aim was to study the hydraulic block scenarios in the water source land conservation zone in Jinshu Bay so as to ensure the water quality in the water sources in Jinshu Bay.[Method] By dint of one dimension water amount and water quality mode in the river net in Taihu,the water flow movement characteristics and pollutants transportation rules in the water sources areas in Jinshu Bay under five kinds of hydraulic block scenarios were compared and discussed.[Result] After demolishing the temporary soil dam in the water source conservation zone in Jinshu Bay,water amount and pollutants increased and water quality deteriorated.It was necessary to take certain hydraulic power to block and control the pollutants in the preservation area;after demolishing the dam,there was less water amount and pollutants.The water quality improved significantly.The hydraulic block facility in the preservation area and its surroundings were all releasing and not introducing;the one along the mouth of the river of Mentianji Gang,Jinshugang and Longtanggang were introducing and not releasing,which only restricted poor-quality water in Beijing-Hangzhou Canal and Huguang Canal flowing into the conservation zone.The water into the conservation zone was all from Gonghu.The water mobility within the conservation zone was good.The regional water quality improved to the largest scale.[Conclusion] Judging from the water flow movement characteristics and pollutants transportation rules in Jinshu Bay,the fifth proposal was more appropriate.

A Self-assembled T4(2)5(2) Water Tape Stabilized by a Nickel(II) Complex with L-cysteic Acid

An interesting T4（2）5（2） water tape formed by fused cyclic water pentamers and tetramer was self-assembled in a new inorganic host [Ni（L）（phen）2]·5H2O （L = L-cysteic acid） and characterized by X-ray diffraction. Each [Ni（L）（phen）2] molecule crystallizes with five water molecules with a molecular formula of [Ni（L）（phen）2]·5H2O. The T4（2）5（2） water tape and [Ni（L）（phen）2] molecules assemble into a network of water tapes sandwiched between [Ni（L）- （phen）2] tapes. The network is stabilized by π-π stacking between [Ni（L）（phen）2] molecules and three types of hydrogen-bonding interactions between [Ni（L）（phen）2] molecules, water molecules, and water and [Ni（L）（phen）2] molecules.

A Novel Zn(Ⅱ)Complex with 1D Supramolecular Water Tape Formed by Cyclic Tetrameric Water Clusters

A new mixed-ligand Zn（II） complex, [Zn（4,4′-bipy）2（H2O）4]-2ANS·6H2O （1, 4,4′- bipy = 4,4′-bipyridine, HANS = 2-aminonaphthalene-l-sulfonic acid）, has been isolated and structurally characterized by single-crystal X-ray diffwaction, FT-IR spectrum, TG and elemental analysis. It crystallizes in the monoclinic system, space group P2 1/c with a = 12.4852（8）, b = 18.3163（12）, c = 10.9707（7） A, β = 114.2600（10）°, V= 2287.3（3） A3, Dc = 1.455 g/cm3, Mr = 1002.37, Z = 2, F（000） = 1048,μ = 0.704 mm＂1, the final R = 0.0408 and wR = 0.962 for 4029 observed reflections with I 〉 2σ（I）. Interestingly, an unusual one-dimensional （1D） water tape with cyclic tetrameric water clusters can be observed in 1, which are further trapped via Zn-O coordination bonds exhibiting a 2D Zn（Ⅱ）-water layer. These 2D Zn（Ⅱ）-water layers are stacked together into a 3D interdigitated supramolecular architecture via weak π…π interactions, in which free ANS anions are tightly filled by hydrogen-bonding interactions. Thus, π…π and classical hydrogen-bonding interactions are fotmd as main driving forces to stabilize the 2D Zn（Ⅱ）-water layers.

断块油藏高含水井关井后剩余油再动用运移规律微观模拟

基于微观可视化光刻玻璃模型,从微观角度定性、定量研究了断块油藏高含水井关井后剩余油再动用运移规律,并开展了影响因素分析。结果表明:水驱后关井期间剩余油再动用类型主要为滴状、柱状和簇状。关井期间剩余油会沿模型倾斜方向向高部位运移聚集,有利于后续水驱阶段进一步提高驱油效率。地层倾角的增大、原油黏度的减小有利于剩余油再动用;关井时间的增加有利于剩余油向高部位采出端接近聚集;后续水驱阶段注入速度的增大会增加波及面积。

福州挡水檐装饰文化的民俗学考察

福州挡水檐的装饰蕴含着极为丰富的民俗文化信息,其透析出来的符号形式、审美风尚、世俗追求与福州当地的民俗文化具有潜质同构的关系,形成以装饰为特征的综合文化现象。因此,对福州挡水檐装饰的具象特征研究,存在其更本质的社会民俗、信仰民俗、游艺民俗等因素是构成其装饰形式、题材的完整逻辑维度,映射出福州人民客观生活的、主观内在的、叙事抒情的民俗文化。

塔里木盆地塔河北部“过溶蚀残留型”断溶体发育特征及其成因

为了研究塔里木盆地塔河北部强剥蚀区海西早期古岩溶洞穴发育特征,用古地貌恢复、岩溶水系统分析、测井-岩心洞穴识别和地震属性刻画等方法进行了YQ5井区的洞穴类型样式识别、缝洞结构刻画和洞穴成因演化研究。研究结果表明:YQ5井区在塔河油田Ⅱ号和Ⅲ号古岩溶台地北部的地势平缓区,总体为多期次岩溶叠加改造后的残留地貌,主要发育幅差较小的溶峰洼地、溶丘洼地和溶丘平原,南部发育NE向展布的峰丛垄脊沟谷。与塔河油田主体区及斜坡区不同,YQ5井区地下和地表水系的流向与地貌趋势不一致,岩溶水系统遭受构造作用破坏,导致补给、径流和排泄的岩溶水循环过程不完整。YQ5井区主要发育暗河型洞穴和“过溶蚀残留型”断溶体。暗河型洞穴充填较为严重,洞穴的有效储集空间受到破坏,影响油气开发效果。岩溶台地的构造抬升造成区域侵蚀基准面的下降,顺走滑断裂的垂向侵蚀作用有利于“过溶蚀残留型”断溶体的持续发育和保存,油气开发效果好。“过溶蚀残留型”断溶体的发育主控因素为走滑断裂、地层剥蚀强度和负向地貌。与塔河古岩溶台地演化过程一致,YQ5井区的岩溶演化经历深切曲流期、岩溶改造期和下渗断溶期3个阶段。暗河型洞穴被持续改造破坏,断溶体则持续建造。

断块油藏注采耦合提高采收率机理及矿场实践

针对渤海湾盆地济阳坳陷东营凹陷古近系断块油藏水驱开发后期流线固定导致注入水无效循环的问题,基于渗流力学和油藏工程原理,通过室内物模模拟和油藏数值模拟,提出了“细分开发层系、轮注轮采”的注采耦合开发调整技术,并验证了该技术可提高采收率的原理。研究结果表明:(1)利用注采耦合开发技术建立的“注入期间的高渗通道与低渗通道吸水量比模型”和“采油期间主流线和非主流线产油量比模型”均揭示了“改变压力场促进渗流场调整,实现均匀注入和均匀采出,扩大水驱波及系数和增加驱油效率”的注采耦合渗流力学机制。(2)注采耦合技术可以实现“扩大波及系数、增加驱油效率”,起到类似“调剖”的作用,高含水期通过此项技术可将低渗透岩心的分流率由1.0%提到18.6%,模型驱替更均衡;经过2个轮次的注采耦合调整,高、低渗透岩心的原油采收率分别提高了10.3%和16.1%。(3)研究区D断块古近系沙河街组沙二段Es236含油小层油藏注采耦合开发数值模拟结果显示,主流线和非主流线驱替更均匀,两者压力梯度极差由2.3下降至1.4。经过3个轮次注采耦合开发调整,沙二段3—6砂层组油藏平均综合含水率下降了3.2%,累计增油1 760 t,提高原油采收率2.1%,增油降水效果显著。

江苏油田复杂小断块高含水油藏注采井网优化技术

江苏油田复杂小断块油藏经过长期的注水开发后,目前处于中高含水开发期。现阶段储层非均质性对注采井网的影响更加突出,局部存在低效无效注水循环问题,亟需优化调整注采井网。根据非均质油藏剩余油富集类型和影响因素,在原井网基础上,利用油藏数值模拟方法,开展相控条件下的注采井网优化技术政策研究。根据模拟结果,确立了抽稀井网和转注高含水油井两种注采井网优化技术的政策界限,指导陈2断块、韦2断块注采井网优化调整,取得了良好的应用效果,为改善高含水油藏水驱开发效果提供了技术支撑。

陆相页岩储集层含水饱和度测井计算方法——以川东南复兴区块凉高山组为例

陆相页岩储集层具有低孔特低渗特征,其黏土矿物含量高,岩石组成变化快,地层非均质性强,利用传统阿尔奇公式及常规数理统计模型计算的含水饱和度误差大。为提高陆相页岩储集层含水饱和度计算精度,以川东南复兴区块下侏罗统凉高山组页岩为例,分析了现有含水饱和度测井计算方法的局限性,阐述了利用阵列声波测井中的纵横波时差与测井密度组合重构的复合波阻抗计算含水饱和度的可行性。在此基础上,提出了陆相页岩储集层含水饱和度计算方法。该方法考虑了岩石矿物的影响,有效避开了电法测井和非电法测井的局限性,提高了适用性。在川东南复兴区块多口井凉高山组页岩储集层的应用效果好,计算得到的含水饱和度与岩心分析含水饱和度较吻合,绝对误差为1.3%~2.2%,满足测井评价要求。

基于层间截流封堵技术的矿井滞后突水治理

结合临汾市某矿突水治理实例,在分析构造、底板扰动破坏、隐伏导水通道基础上,进一步研究了残余有效隔水层在底板水压、两侧煤柱以及采空区中部顶板垮落压实综合作用下二次破坏的形式,确定此次突水是在底板扰动破坏和底板隐伏导水构造基础上,残余有效隔水层受底板水压向上牵引应力和煤柱支撑影响发生二次破坏形成导水通道造成的。并据此提出层间截流封堵治理方案,以110 m水平进尺快速揭露导水通道,注浆15500 t,突水量降低94%,水位抬升14.725 m,成功堵水。可为类似矿井水害治理提供有益借鉴。

基于频域反射法的高压电缆阻水缓冲层缺陷定位研究

为了获取高压电缆缓冲层缺陷的位置信息,本文首先根据缓冲层表面形貌特征将缓冲层状态划分为干燥态、受潮态、腐蚀态以及腐蚀烧蚀态,通过薄片样本研究了缓冲层从干燥态到腐蚀烧蚀态这一缺陷发展过程中体积电阻率和相对介电常数的变化规律。然后推导了高压电缆传输线网络中的分布电容以及分布电导的计算公式,评估了FDR法应用于高压电缆缓冲层缺陷定位的可行性。最后在实验室中搭建了长电缆实验平台,研究了频域反射法定位缓冲层缺陷的有效性。结果表明:缓冲层缺陷的发展主要影响高压电缆的分布电容,产生阻抗不连续点。FDR能够实现对缓冲层受潮及缺陷的定位,但对于腐蚀缺陷及烧蚀缺陷的进一步区分还需结合其他状态检测手段。

渤南油田罗36块减缓自然递减治理对策研究

罗36块位于渤南油田十区,为四周被断层夹持的小型狭长断块。面对罗36块裂缝发育,注水易窜与能量低的矛盾,在沙四段原油性质较差,油稠、凝固点高的影响下,自然递减率逐年上升,成为困扰罗36块可持续发展的主要因素。自然递减率越大,老井产量下降速度越快,直接影响到各项开发指标及经济效益。确定储层非均质性强和原油粘度高是影响单井减产的两大主因。针对此两类问题,制定治理对策,通过堵水调驱、挤入降粘剂等一系列调整治理,罗36块自然递减率呈现向好趋势,自然递减率由8.58%降低为3.1%,开发指标得到提升,储量得以有效动用。

准噶尔盆地东部北10井区中深层稠油CO_(2)非混相驱油技术

准噶尔盆地东部北10井区头屯河组油藏具有埋藏深、原油黏度大、储层强水敏的特点,自探明以来一直未获得有效动用。为了解决油藏难动用的难题进行了CO_(2)-稠油实验,在实验结果的基础上,根据试验区生产现状提出“非混相驱+吞吐”措施,利用数值模拟手段优化生产参数得到最优方案并预测出生产指标。结果表明:地层稠油注入CO_(2)后原油体积膨胀和黏度降低的能力大幅增强,是提高采收率的主要机理;井区稠油CO_(2)驱替方式为非混相驱,驱替过程中CO_(2)先以溶解和扩散作用为主,待建立驱替通道后才开始产出原油,采收率为29.60%;试验区非混相驱初期见效慢,为加快受效提出“油井吞吐”措施,数值模拟预测非混相驱配合3轮油井吞吐生产,最终采收率可达21.0%,解决了研究区油藏难动用的难题。研究成果对中深层强水敏稠油油藏的动用具有一定的借鉴意义。