油水井压裂技术发展趋势研究

油田开发中,油水井压裂技术是一项重要的技术手段,能够增加储层的渗透性和产量。随着油田复杂性的不断增加,传统的压裂技术已经无法满足对高效、可持续的增产需求。因此,油水井压裂技术的创新势在必行,此次将重点分析油水井压裂技术创新以及发展趋势。

低渗透砂岩油藏水井压裂参数优化数值模拟研究

利用油藏—裂缝耦合方法,建立了一种油、水两相三维油藏裂缝数值模型,采用对裂缝进行矩形网格剖分、与油藏连接处进行PEBI网格剖分相结合的方法,可以实现对不同井网条件下生产井压裂效果进行数值模拟研究。以胜利油田史深100低渗透断块油藏为例,在反九点法井网条件下,提出综合效果评价指标,对注水井压裂参数设计进行了优化计算。研究结果为低渗透油藏注水井压裂设计和效果评价提供了一种研究手段,对于提高低渗透油田注水效果具有实际意义。

基于油藏—裂缝耦合的低渗油藏水井压裂数值模拟研究

利用油藏—裂缝耦合技术,采用对水力压裂裂缝进行矩形网格剖分、与油藏连接处进行PEBI网格剖分相结合的方法,建立油、水两相三维油藏裂缝数值模拟器。利用此数值模拟器,模拟研究了不同条件下水井压裂对注采井组整体开发效果的影响,并利用正交方差分析方法对水井压裂增注效果的主要影响因素进行了显著性评价,提出了适合进行水井压裂增注的油藏条件。以江苏油田H10低渗透断块油藏为例,提出综合效果评价参数,对实际油藏注水井压裂参数设计进行了优化。研究结果为低渗透油藏注水井压裂设计和增注效果评价提供了一种研究手段,对于提高低渗透油田注水效果具有实际意义。

周期注水与注水井压裂相结合在敖南油田应用的机理研究

周期注水及注水井压裂技术作为改善注水开发效果的两项重要措施,在油田开发中起着很大的作用,但在应用过程中也存在一些问题。本文通过对周期注水与注水井压裂机理及其问题的分析,提出了周期注水与水井压裂结合的调整办法,降低高压注水井注水压力及扩大注水波及体积,改善油田开发效果。

热酸助排技术在E3^1油藏水井压裂中的应用

本文主要介绍了热酸助排技术在E3^1油藏水井压裂中的应用。通过压前设计思路分析、现场施工、压后效果证明热酸助排技术应用在E3^1油藏水井压裂中效果很好，具有广阔的推广前景。

无线射频压裂滑套系统模拟试验研究

将无线射频识别(RFID)技术应用到油水井压裂中,能够很好地解决现有压裂滑套存在的压裂级数受限、操作非智能等诸多问题。因井下工况复杂,理论分析与实际应用差别较大,为进一步系统地探究井下无线射频系统的开发应用,使用三维软件设计无线射频滑套模拟试验台,对标签的运动状态进行理论分析,并建立室内模拟试验平台,系统地进行井下相关试验。试验结果表明:标签选择有铁氧体磁芯,且天线绕制形式选用单层螺线管线圈,可以提高整个系统的性能;在系统电感值相同的情况下,单层螺线管天线轴向长度对阅读器模块能识别的标签最大通过速度有积极的影响;标签天线线圈与阅读器天线线圈平面之间的角度也会影响标签的识别率。研究结果对井下无线射频系统的开发应用具有一定的指导作用。

低渗透油田注水井有效压裂研究

由于特低渗透油藏储层的物性差、孔隙孔喉狭窄,致使注水井地层吸水能力差,导致井口压力不断提高,可能达到甚至超过地面注水管线的临界压力,给油田注水开发带来极大困难。近几年,某油田针对注水压力高的问题,实施了注水井压裂,但整体效果较差。通过对整体压裂优化技术研究,获得油井压裂后产量递减规律,分析油田压裂的方法与潜力,为某油田在目前开发条件下的注水井压裂改造的有效性提供科学依据。

榆树林油田东18井区水井裂缝参数的优化

针对大庆榆树林油田水井压裂方案存在的问题，根据东18井区油藏地质和现有开发井网与裂缝方位，采用eclipse油藏模拟软件和“等效导流能力”方法，进行了多参数下压裂增产增注的油藏模拟计算与分析。结果显示，在储层有效渗透率分别为0．1×10-3，0．3×10-3，0．5×10-3和0．8×10-3μm2时，水井裂缝长度分别为50．0，37．5，30．0和20．0m，一类油井分别为80，70，60和50m，二类油井分别为120，100，90和80m，三类油井分别为100，90，80和70m；油、水井裂缝导流能力在20～30μm2·cm。低渗油藏水井裂缝长度应严格控制，以免水窜，要求的导流能力相对较低。模拟井组优化的水井裂缝参数可为榆树林油田水井压裂施工方案提供参考。

对应精细控制压裂技术在低渗透油藏薄差油层的应用

针对低渗透油田薄差油层薄互层多、连续性差、注采关系不完善等问题,以提高薄差油层有效动用为目标,开展了薄差油层对应精细控制压裂改造技术应用。创新油水井对应精细控制压裂技术应用,将改造方式由单井点常规压裂转变为油水井组同时压裂改造,将改造对象由双封单卡多层段笼统压裂转变为单砂体对应压裂改造,将裂缝形式由常规单缝延伸转变为树枝状裂缝系统,将压裂砂量由常规固定用量转变为单砂体个性化用量。现场试验8个井组,平均单井日增油3.1 t,增油强度1.1 t/(d·m),平均有效期266 d,技术效果明显优越于常规油井单井压裂。通过对应精细控制压裂技术的创新应用,大幅度提高了薄差油层的动用程度,对低渗透油田开发具有重要的指导意义。

榆树林特低渗透油田注水井清水压裂技术研究

目前大庆榆树林油田注水井投注时,基本采取不压裂投注方式注水。由于储层特低渗透、岩层致密,孔喉细小,注水井地层吸水能力差,造成注水困难,本文通过分析水井压裂的影响因素,结合目前的储层性质,完成榆树林油田水井压裂可行性分析与具体实施方法,给出了清水压裂的施工参数优化及实施思路。

Pressure transient analysis of a finite-conductivity multiple fractured horizontal well in linear composite gas reservoirs

Faulted gas reservoirs are very common in reality,where some linear leaky faults divide the gas reservoir into several reservoir regions with distinct physical properties.This kind of gas reservoirs is also known as linear composite(LC)gas reservoirs.Although some analytical/semi-analytical models have been proposed to investigate pressure behaviors of producing wells in LC reservoirs based on the linear composite ideas,almost all of them focus on vertical wells and studies on multiple fractured horizontal wells are rare.After the pressure wave arrives at the leaky fault,pressure behaviors of multiple fractured horizontal wells will be affected by the leaky faults.Understanding the effect of leaky faults on pressure behaviors of multiple fractured horizontal wells is critical to the development design.Therefore,a semi-analytical model of finite-conductivity multiple fractured horizontal(FCMFH)wells in LC gas reservoirs is established based on Laplace-space superposition principle and fracture discrete method.The proposed model is validated against commercial numerical simulator.Type curves are obtained to study pressure characteristics and identify flow regimes.The effects of some parameters on type curves are discussed.The proposed model will have a profound effect on developing analytical/semi-analytical models for other complex well types in LC gas reservoirs.

Reservoir reconstruction technologies for coalbed methane recovery in deep and multiple seams

Multiple coal seams widely develop in the deep Chinese coal-bearing strata. Ground in situ stress and coal seam gas pressure increase continuously with the increase of the mining depth, and coal and gas outburst disasters become increasingly severe. When the coal is very deep, the gas content and pressure will elevate and thus coal seams tends to outburst-prone seams. The safety and economics of exploited firstmined coal seams are tremendously restricted. Meanwhile, the multiple seams occurrence conditions resulted in different methane pressure systems in the coal-bearing strata, which made the reservoir reconstruction of coal difficult. Given the characteristics of low saturation, low permeability, strong anisotropy and soft coal of Chinese coal seams, a single hydraulic fracturing surface well for reservoir reconstruction to pre-drain the coalbed methane(CBM) of multiple seams concurrently under the different gas pressure systems has not yet gained any breakthroughs. Based on analyses of the main features of deep CBM reservoirs in China, current gas control methods and the existing challenges in deep and multiple seams, we proposed a new technology for deep CBM reservoir reconstruction to realize simultaneous high-efficiency coal mining and gas extraction. In particular, we determined the first-mined seam according to the principles of effectiveness and economics, and used hydraulic fracturing surface well to reconstruct the first-mined seam which enlarges the selection range of the first-mined seam. During the process of mining first-mined seam, adjacent coal seams could be reconstructed under the mining effect which promoted high-efficiency pressure relief gas extraction by using spatial and comprehensive gas drainage methods(combination of underground and ground CBM extraction methods). A typical integrated reservoir reconstruction technology, ‘‘One well for triple use", was detailed introduced and successfully applied in the Luling coal mine. The application showed that the proposed technology could effectively promote coal mining safety and simultaneously high-efficiency gas extraction.

Rate decline analysis of multiple fractured horizontal well in shale reservoir with triple continuum

Multiple fractured horizontal well(MFHW) is widely applied in the development of shale gas. To investigate the gas flow characteristics in shale, based on a new dual mechanism triple continuum model, an analytical solution for MFHW surrounded by stimulated reservoir volume(SRV) was presented. Pressure and pressure derivative curves were used to identify the characteristics of flow regimes in shale. Blasingame type curves were established to evaluate the effects of sensitive parameters on rate decline curves, which indicates that the whole flow regimes could be divided into transient flow, feeding flow, and pseudo steady state flow. In feeding flow regime, the production of gas well is gradually fed by adsorbed gases in sub matrix, and free gases in matrix. The proportion of different gas sources to well production is determined by such parameters as storability ratios of triple continuum, transmissibility coefficients controlled by dual flow mechanism and fracture conductivity.

Impact Factors on Fracturing Results of Coal Seams and Appropriate Countermeasures

Hydraulic fracturing is one of the efficient means for the abundant low-permeability CBM （coal-bed methane） reserves in China, however, due to the unique features of coal seams （i.e., low temperature, strong adsorption and abnormal development of natural fracture systems） as compared with the conventional reservoirs, the fractures propagate is difficult and the risk of damage to coal seam itself and the hydraulic fractures would be extremely high in the course of fracturing. As a result, losses would be suffered on the post-frac production of CBM wells.With the mean of numerical simulation, in this paper, the main factors have impact on the post-frac results as well as the extent to which the impact is brought were researched, and the technical solutions for the improvement of the fracturing performance was put forwards.

STUDY ON THE SMALL CRACKS OF COVER STRATA AFTER THE COMBINED MINING IN THE THIN SEAMS

By using the continuous exploration system with multi-pipeline in the borehole, the failure cracks of cover strata (specially, the small cracks developing) after the combined mining of 16, 17 thin seams of the 4th mining block in Zhaopo Mine is explored. After that, the researching result is considered as the output and the testing result of rock mechanics parameters is considered as the verifying data, the back analysis is made with the conception of the point safety degree. The relative height of the crack developing is obtaied. So, the evaluating of the safety of 16, 17 seams combined mining under the gob water with extreme distance is made and the mining has been safety. The scientific basis is provided for the evaluating of the mining safety with the similar conditions.

An optimal fracture geometry design method of fractured horizontal wells in heterogeneous tight gas reservoirs

In this work, the unified fracture design （UFD） is extended for the first time to the fractured horizontal wells in heterogeneous closed box-shaped tight gas reservoirs. Utilizing the direct boundary element method and influence function, the dimensionless fracture productivity index is obtained and expressed in the function of proppant volume and fracture geometry at the pseu- do-steady state. With the iterative method, the effectively propped permeability, kfe, is corrected using the i^-situ Reynolds number, NRe. The goal of this paper is to present a new UFD extension to design the proppant volume and the optimal fracture geometry. The results show that there exists an optimal proppant volume for a certain reservoir. The small aspect ratio （yJXe） and high permeability reservoirs need short and wide fractures to diminish the non-Darcy effect. On the contrary, long and narrow fractures are required for the large aspect ratio and low permeability reservoirs. A small proppant volame is prone to creating long fractures, while a relatively large proppant volume creates wide fractures. The new extension can be used to evaluate the previous fracture parameters and design the following fracture parameters of the fractured horizontal well in heterogeneous tight gas reservoirs, with the non-Darcy effect taken into account.

Numerical modeling of simultaneous hydraulic fracturing in the mode of multi-well pads

In order to investigate propagation regularity of hydraulic fractures in the mode of multi-well pads, numerical modeling of simultaneous hydraulic fracturing of multiple wells was conducted. The mathematical model was established coupling rock deformation with fluid flow in the fractures and wellbores. And then the model was solved by displacement discontinuity method coupling with implicit level set method. The implicit method was based on fracture tip asymptotical solution and used to determine fracture growth length. Simulation results showed that when multiple wells were fractured simultaneously, adjacent fractures might propagate towards each other, showing an effect of attraction other than repulsion. Fracture spacing and well spacing had significant influence on the propagation path and geometry of multiple fractures. Furthermore, when multiple wells were fractured simultaneously, stress reversal regions had a large area, and stress reversal regions were distributed not only in the area between fractures but also on the outside of them. The area of stress reversal regions was related to fracture spacing and well spacing. Results indicated that multi-well fracturing induced larger area of stress reversal regions than one-well fracturing, which was beneficial to generating complex fracture network in unconventional reservoirs.