非线性井底流压条件下煤层气试验井产能预测模型及应用

为了探索水力压裂条件下焦作"三软"(软煤、软顶和软底)矿区低渗煤层煤层气渗透机理及产出规律,首先基于储层压裂缝扩展模型,根据压裂后裂缝孔隙度与渗透率的关系,建立了储层压裂渗透模型,着重考虑了井底流压的非线性动态变化对煤层气产出的影响,建立了产能预测模型,并进行了试验单井的应用及分析;其次,根据压裂缝几何参数与井底流压,计算得到试验期理论产气量,通过历史拟合法将试验期实采数据、试验期理论产出及试验期模拟产出3者进行对比分析,从而验证了产能预测模型的正确性;最后,结合相关参数,运用产能预测模型对矿区GW-002试验井进行生产期2 450 d的产能预测及经济评价期内的采收率计算。结果表明,该试验井生产期内平均日产气量可达587 m~3,累计产气量可达1.05×10~6 m~3,经济评价期内采收率可达32.86%,满足了煤层气开采技术要求。研究成果可用于指导"三软"矿区煤层气井压裂抽采实践与产能预测。     

深部煤层气井排采特征及产能控制因素分析

根据鄂尔多斯盆地某区块深部煤层气井生产资料,分析深部煤层气井在排采初期的气水产出特征;研究影响深部煤层气井产能的地质和工程主要因素,基于产能主控因素提出研究区深部煤层气开发建议.结果表明:深部煤层气井在排采初期产能偏低,影响产气效果的地质因素主要包括构造部位、煤层埋深、含气量及水动力条件,工程因素主要包括压裂参数、开采层数和抽采制度;开发时应注意控制压裂液排量高于7.75m3/min,保持30~40m3的加砂量,并根据产气变化及时调节泵冲次,调节幅度以小于0.05次/min为宜;工程前期设计和后期操作要与地质情况紧密结合,充分发挥两者对产能控制的最大优势.     

煤层气储层保护钻完井工艺技术探讨

分析钻完井过程中煤层气储层的损害机理,从井身结构设计、钻井方式选择、钻井参数优化、起下钻计算等方面,提出保护煤层气储层的钻井工艺技术,并对煤层气井固完井工艺技术进行了探讨,对于保护煤层气储层,提高煤层气开发效率具有一定的指导意义。     

白家海凸起深层煤层气压裂试气实践与认识

埋深超过1 000m的深层煤层气因其赋存状态研究较少,产出条件又不同于浅层煤层气压裂试气工艺要求,勘探开发技术难度大。基于准噶尔盆地东部白家海地区彩A井和彩B井的压裂实践,认为白家海地区煤层埋深大于1 500m,煤层气符合中煤阶肥煤特征,储层富集以游离气为主,其压裂试气宜采用"低粘液、大排量、大液量、高砂比"压裂改造措施和"螺杆泵+直读压力计+套管控压"的排液工艺。     

滇东黔西老厂矿区雨汪区块煤层气井产能特征及其影响因素

为研究多煤层发育区影响煤层气井产能的主要因素,以滇东黔西老厂矿区雨汪区块为研究对象,基于区内煤层气地质及气井排采资料,分析区内煤层气井产气、产水特征,探讨影响煤层气井产能的关键因素。研究结果表明,雨汪区块中-低产煤层气井数量占总井数的73%,影响气井产能的主要包括地质和排采因素,其中,地质因素主要为地应力和渗透率,排采因素主要为产水速率和停井次数。建议本区煤层气勘探开发应首选中-低地应力、渗透率较高的部位或层段,气井排采初期产水量需控制在1.5～3 m~3/d,见气后产水量控制在1～1.8 m~3/d,排采期间尽量减少停井次数。     

一门新兴边缘学科的重要著作《煤层气地质学与勘探开发》出版发行

本刊讯　焦作工学院苏现波、陈江峰、孙俊民、程昭斌等编著的《煤层气地质学与勘探开发》一书于2001年2月由科学出版社出版发行．著名煤田地质学家、中国工程院院士、本刊顾问韩德馨教授为该书作序。 　　该书根据国内外煤层气生产与科研资料,结合作者近期的科研成果,从煤层气的成因、储层、赋存、储层数值模拟和综合地质评价等方面论述了煤层气地质学的基本理论和研究方法。同时对目前在煤层气勘探开发中常用的工艺技术进行了详细介绍,包括钻井、测井、完井、固井、试井、储层强化和开发等方面的理论基础和工艺,并对目前仍在探索阶段的一些工艺技术进行了简要介绍。 （谢定均)     

江汉油区侧钻井井位优选技术与应用

通过油藏的再认识,根据剩余油分布特征及地面井筒条件,建立和规范了地质设计标准,在对报废井及方案停产井进行大量调查的基础上,优选并组织实施了4口侧钻井位。其中3口井恢复日产油20t,恢复可采储量2．0×10^4t,恢复产能0．45×10^4t,初步形成了江汉油区侧钻井选井原则及挖潜模式。     

高煤级煤储层水力压裂裂缝扩展模型研究

为了研究煤层气井水力压裂后的裂缝扩展规律,以沁水盆地南部煤层气井为例,基于区内煤储层的物性特征和水力压裂工程实践,根据水力压裂原理,采用数值分析的方法,探讨了研究区的煤层气井水力压裂后的裂缝形态与裂缝展布规律,提出了研究区煤层气井压裂过程中的综合滤失系数计算方法,构建了高煤级煤储层水力压裂的裂缝扩展模型,并进行了验证.研究结果表明:区内煤层气井压裂后形成的裂缝一般扩展到顶底板的泥岩中,且以垂直缝为主,裂缝形态符合KGD模型.区内常规压裂井的裂缝长为47.8～177.0m,平均90.6m.裂缝缝宽为0.013～0.049m,平均0.028m.模型计算结果与实测值、生产实践较为吻合.     

沁南煤层气合层排采有利开发地质条件

针对沁水盆地南部山西组3#与太原组15#煤层煤层气合层排采"整体产能低"及"区域性差异大"的产能特征,探索适合合层排采的有利开发地质条件.以沁水盆地南部22口合层排采煤层气井的产气、产水资料,试井储层压力、试井渗透率、含气量等测试数据为依据,采用地质研究与探采测试数据分析相结合的方法,分析了不同地质因素对合层排采井产能特征的控制作用,提出了适合沁南3#与15#煤层合层排采的有利开发地质条件的参数指标.结果表明:平均埋深为500~650m;平均含气量大于14m3/t;储层压力梯度差小于0.08 MPa/hm;渗透率较高且差值不超过1mD;3#煤层的临界解吸压力高于15#煤层,且差值小于0.9MPa,满足合层排采的地质条件要求,可为今后进行规模性开发提供借鉴.     

煤层气垂直井重复水力压裂综合评价方法研究

系统分析了重复水力压裂选井的主要影响因素,建立了重复水力压裂选井事故树模型;根据多层次模糊数学综合评价方法结合事故树模型,建立了煤层气垂直井重复水力压裂选井评价指标体系.根据评价指标体系,对沁水盆地东南樊庄区块部分产气效果不好的煤层气井能否对二次压裂进行评价.结果表明,该方法能较好地为现场煤层气垂直井重复水力压裂选井提供理论依据,投资风险大大降低.     

Exploitation technology of pressure relief coalbed methane in vertical surface wells in the Huainan coal mining area

Exploitation technology of pressure relief coalbed methane in vertical surface wells is a new method for exploration of gas and coalbed methane exploitation in mining areas with high concentrations of gas, where tectonic coal developed. Studies on vertical surface well technology in the Huainan Coal Mining area play a role in demonstration in the use of clean, new energy re-sources, preventing and reducing coal mine gas accidents and protecting the environment. Based on the practice of gas drainage engineering of pressure relief coalbed methane in vertical surface wells and combined with relative geological and exploration en-gineering theories, the design principles of design and structure of wells of pressure relief coaibed methane in vertical surface wells are studied. The effects of extraction and their causes are discussed and the impact of geological conditions on gas production of the vertical surface wells are analyzed. The results indicate that in mining areas with high concentrations of gas, where tectonic coal developed, a success rate of pressure relief coalbed methane in surface vertical well is high and single well production usually great. But deformation due to coal exploitation could damage boreholes and cause breaks in the connection between aquifers and bore-holes, which could induce a decrease, even a complete halt in gas production of a single well. The design of well site location and wellbore configuration are the key for technology. The development of the geological conditions for coalbed methane have a sig-nificant effect on gas production of coalbed methane wells.     

地面群孔瓦斯抽采技术应用研究

为保证新集一矿突出煤层13-1煤北中央采区的安全开采,先后开采131103、131105等11-2煤层工作面作为保护层。首先在上述两个工作面共布置了6个地面钻孔,建立了地面群孔瓦斯抽采系统,预抽采动区被保护层13-1煤瓦斯。接下来对地面钻孔抽采瓦斯参数进行了考察,主要包括基于示踪技术考察了131105工作面采动卸压地面钻孔走向及倾向瓦斯抽采半径,统计分析被保护层瓦斯抽采率,同时就地面群孔与井下底板巷穿层钻孔瓦斯抽采两种方法进行了抽采率、工程费用等方面的对比。研究结果表明：新集一矿的地层条件下地面钻孔抽采煤层卸压瓦斯沿煤层倾向和走向的抽采半径分别不小于160m和240m;采动区地面群孔瓦斯抽采率达35%以上;地面钻孔相对比井下底板巷,在抽采瓦斯方面具有技术上可靠、安全、经济等优点。     

绒囊钻井液在煤层气延3U1-P井的应用

煤层气延3U1-P井属于排采井,在三开钻井施工中,选用绒囊钻井液在煤层段水平钻进,通过加入成核剂、成膜剂、囊层剂、绒毛剂等形成绒囊钻井液体系,保持钻井液较低的密度,保持井壁稳定、保护煤层,满足了钻井需要和井下安全、保证无掉块垮塌等现象。     

Evolution and application of in-seam drilling for gas drainage

The presence of seam gas in the form of methane or carbon dioxide presents a hazard to underground coal mining operations. In-seam drilling has been undertaken for the past three decades for gas drainage to reduce the risk of gas outburst and lower the concentrations of seam gas in the underground ventilation. The drilling practices have reflected the standards of the times and have evolved with the development of technology and equipment and the needs to provide a safe mining environment underground. Early practice was to adapt equipment from other fields, with rotary drilling being the only form of drilling available. This form of drainage allowed various levels of gas drainage coverage but with changing emphasis, research and development within the coal industry has created specific equipment, technology and practices to accurately place in-seam boreholes to provide efficient and effective gas drainage. Research into gas content determination established a standard for the process and safe levels for mining operations to continue. Surveying technology improved from the wire-line, single-shot Eastman survey instruments which was time-dependent on borehole depth to electronic instruments located in the drill string which transmitted accurate survey data to the drilling crew without time delays. This allowed improved directional control and increased drilling rates. Directional drilling technology has now been established as the industry standard to provide effective gas drainage drilling. Exploration was identified as an additional benefit with directional drilling as it has the ability to provide exploration data from long boreholes. The ability of the technology to provide safe and reliable means to investigate the need for inrush protection and water drainage ahead of mining has been established. Directional drilling technology has now been introduced to the Chinese coal industry for gas drainage through a practice of auditing, design, supply, training and ongoing support. Experienced drilling crews can offer site specific gas drainage drilling services utilising the latest equipment and technology.     

Proactive interburden fracturing using UIS drilling with validation monitoring

A series of gas inrush events occurred during development at Grosvenor Mine resulting in exposure to elevated levels of methane at the production face. A total of 22 gas inrush events occurred, with between15 and 130 m3 of methane released during each event. The presence of an undrained seam in the immediate floor, geotechnical characteristics of the floor, and the stress environment all contributed to these dynamic floor events, while the geological characteristics of the seam below, such as the seam thickness and ash content of 75%, prevented effective predrainage. However, events only occurred in headings mined parallel to the principal horizontal stress direction. In cut-throughs(C/T) perpendicular to the principal stress direction no events occurred, and higher methane levels were observed at the production face. The solution to preventing the gas inrush events involved creating a conduit in the interburden between the mined seam and the seam in the immediate floor to allow the gas to be drained during the development of the headings, as occurred in the cut-throughs(cut-through and cross-cut are regional terms that are analogous). A series of underground inseam(UIS) holes were drilled using the directional drill rig with the aim of fracturing this interburden ahead of the face and promote floor failure to allow the gas to release consistently. The floor fracturing was conducted using water pressure generated from a longwall salvage pump, with the current UIS drilling equipment retrofitted with a series of subs, packers and a fracturing tool. The packers and the fracturing tool were shifted to desired locations along the drilled UIS borehole to achieve the required fracture. The fractures were monitored using a proving hole and with a HYDAC data logger attached to the salvage pack, with the results analysed on the surface to ensure connectivity to the working seam.     

CFD simulations for longwall gas drainage design optimisation

Computational fluid dynamics(CFD) simulation is an effective approach to develop and optimise gas drainage design for underground longwall coal mining. As part of the project supported by the Australian Government Coal Mining Abatement Technology Support Package(CMATSP), threedimensional CFD simulations were conducted to test and optimise a conceptual design which proposes using horizontal boreholes to replace vertical boreholes at an underground coal mine in Australia.Drainage performance between a vertical borehole and a horizontal borehole was first carried out to compare their capacity and effectiveness. Then a series of cases with different horizontal borehole designs were simulated to optimise borehole configuration parameters such as location, diameter, and number of boreholes. The study shows that the horizontal borehole is able to create low pressure sinks that protect the workings from goaf gas ingresses by changing goaf gas flow directions, and that it has the advantage to continuously maintain such low pressure sinks near the tailgate as the longwall advances. An example of optimising horizontal borehole locations in the longwall lateral direction is also given in this paper.     

基于卸压开采的下向穿层钻孔抽采瓦斯技术

为了实现下伏被保护层的卸压瓦斯抽采最大化,本文提出了保护层开采采用“Y”型通风沿空留巷技术,同时配合下向穿层钻孔的立体式抽采瓦斯技术,优化确定了下向钻孔的技术参数、施工时间、粉尘防治等工艺难题。工程实践表明,下向穿层钻孔单孔抽采瓦斯纯量可达0．2m^3/min,最大约0．45m^3/min,浓度高达60～90％,高效稳定时间约20～30d,可实现卸压瓦斯的抽采最大化。     

Application of gas wettability alteration to improve methane drainage performance: A case study

Hydraulic fracturing technique is widely used for methane drainage and has achieved good effects in numerous coal mines, but negative effects may occur as the fracturing fluids are absorbed into the coal seam. Gas wettability alteration(GWA) technology can be used as it can enhance the gas and water mobility during dewatering process as a result of capillary pressure change. However, there have been few reported field tests in coal mines using GWA technology. This paper describes a pilot-scale field test in Xinjing coal mine, Yangquan, China. The fluorocarbon surfactants perfluorooctyl methacrylate monomer-containing polymethacrylate(PMP) was used to alter the wettability of coal seam to strong gas-wetness during the hydraulic fracturing process. The study focuses on the comparison of two boreholes(Boreholes #9 and #10) and one other borehole(Borehole #8) with and without using GWA approach. A well-defined monitoring program was established by measuring the dewatering volume of the fracturing fluid and the drainage volume of methane as well as the concentration. The field test results showed that the average methane drainage rates of Boreholes #9(39.28 m~3/d) and #10(51.04 m3/d) with GWA treatment exceeded that of Borehole #8(21.09 m~3/d) without GWA treatment,with an increase of 86.3% and 142.1%, respectively. The average methane concentrations of Boreholes #9(4.05%) and #10(6.18%) were 64.6% and 151.2% higher than that of Borehole #8(2.46%), respectively. On the other hand, the dewatering ratio of Boreholes #9(4.36%) and #10(3.11%) was almost 19 times and 13 times greater than that of Borehole #8(0.22%). These field test results were in agreement with the experimental data. The significant increase in both methane concentration and dewatering ratio demonstrated that GWA technology could be applied for enhanced methane drainage in coal mines. Important lessons learned at Xinjing coal mine might be applied to other coal mines in China and elsewhere.     

超高压水力割缝强化抽采瓦斯技术研究

水力割缝是一种重要的强化瓦斯抽采增透技术,现已开始在低透气性突出煤层应用。为了进一步考察其实际效果,选取新集二矿1煤组220112工作面底抽巷实施了100 MPa超高压水力割缝试验。试验结果表明:割缝后,瓦斯抽采纯量平均0.77 m3/min,是未割缝钻孔的瓦斯抽采纯量(0.34 m~3/min)的2.26倍;1煤层组瓦斯抽采钻孔抽采30、60天的抽采有效半径为5 m、7.5 m,极限抽采半径为8 m,相比水力冲孔、未割缝钻孔抽采有效半径显著增加,超高压水力割缝强化抽采瓦斯技术具有广泛的应用前景。     

基于相控的煤层气藏三维地质建模

煤层气藏是一种非常规天然气藏,与常规天然气藏在赋存方式、物性参数以及开发方式等方面存在较大差异。煤层气藏三维地质模型能够精确描述煤层以及物性参数空间分布,推动煤层气藏的认识由定性向定量的转变,对煤层气藏的开发具有重要意义。以澳大利亚B区块煤层气藏为研究对象,综合应用地质、地震、测井、煤岩取芯分析等资料,分析构造解释的煤层层面、测井精细解释结果以及物性参数精细表征结果;借助Petrel三维地质建模软件,以地震解释煤层顶面构造和断层结果为数据基础,以测井煤层划分结果为约束条件,建立B区块构造模型;在构造建模基础上,以测井资料划分的单井岩相数据为基准,建立煤层相模型;煤层气藏物性参数建模以相控建模理论为指导,以煤层气物性参数表征结果为数据基础,实现干燥无灰基含气量、渗透率、密度、灰分含量、饱和度等物性参数空间分布模拟。在建立的三维地质模型基础上,利用煤层气藏储量计算方法,计算B区块地质储量,确定B区块煤层气有利区优选物性参数及标准,划分煤层气藏有利区。煤层气藏三维地质模型为煤层气藏地质储量计算以及有利区筛选奠定坚实的地质基础,同时也为井型选择与井网布置等后续开发工作提供地质依据。