在澳大利亚Cooper盆地,井眼轨迹、完井和裂缝设计的改变提高了非常规致密气目标的执行力

Raymond L. Johnson, Ruizhi Zhong, Lan Nguyen
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引用次数: 0

摘要

澳大利亚的Cooper盆地受到走滑反应力状态的挑战,对水力压裂处理产生不利影响。在钻井作业中,高偏应力条件会增加井眼破裂,影响测井数据采集,影响固井作业质量。与天然压裂相结合的不利应力条件导致:复杂压裂(具有剪切和次垂直分量);近井压力损失(NWBPL)值高;低渗透率、低模量层(如碳质页岩、互层煤)的增产优先于目标、高模量的致密气砂岩。通常情况下,在过去的Cooper盆地完井以及在昆士兰西南部Windorah槽的案例研究的抵消区域,都使用了直井。我们将介绍两口案例研究井的结果,这两口井与之前的一口直井相匹配,在该直井中,为了提高Cooper盆地Patchawarra致密气藏处理的作业执行力,在正在进行的实验中采用了井眼轨迹、完井和裂缝设计的变化。根据邻井数据,这两口井的最终倾角分别为31°和25°,与最大水平应力方向的方位角小于10°。为了更好地定义测井数据有限、较差或缺失的井段(因为井况困难),钻井数据、随钻测井(LWD)伽马数据、裸眼常规测井和偶极子声波测井,以及之前的一维应力数据与机器学习模型一起使用,以改善应力剖面和储层表征。接下来,沿着井筒进行0°和180°的射孔,分别增加初始流体粘度,以更好地对齐水力裂缝,降低NWBPL。最后,为了验证水平应变,并在对两口井进行增产前校准最终的1D应力剖面,在不同模量的井段和感兴趣的区域进行了诊断性裂缝注入测试(DFIT)。改进后的井眼和射孔对准最大水平应力方向,改善了储层连接,在某些情况下降低了NWBPL,在某些情况下改善了裂缝封闭性。降低注入速度和最小化射孔段,提高了射孔段的针对性;然而,总体裂缝宽度仍然很低,并且对支撑剂的尺寸和浓度仍然很敏感,并且经历了几次筛出。与采用5级处理的直井相比,采用4级和3级处理的井在短期内提高了产量。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Well Trajectory, Completion and Fracture Design Changes Improve Execution for Deep Unconventional Tight Gas Targets in the Cooper Basin, Australia
The Cooper Basin of Australia is challenged by strike-slip to reverse stress regimes, adversely affecting hydraulic fracturing treatments. In drilling, the high deviatory stress conditions increase borehole breakout, affect log acquisition and impact cementing job quality. The non-favourable stress conditions in conjunction with natural fracturing result in: complex fracturing (with shear and sub-vertical components); high near-wellbore pressure loss (NWBPL) values; and stimulation of lower permeability, low modulus intervals (e.g., carbonaceous shales, interbedded coals) in preference to the targeted and higher modulus, tight-gas sandstones. Typically, vertical wells have been employed in past completions of the Cooper Basin as well as in the offsetting areas to the case study in the Windorah Trough, Southwest Queensland. We will present the results from two case study wells offsetting a previous vertical well where well trajectory, completion and fracture design changes were employed in an ongoing experiment to improve job execution for Patchawarra tight gas reservoir treatments in the Cooper Basin. The two wells were directionally deviated at 31° and 25° final inclinations from vertical with azimuth <10 deg from the maximum horizontal stress direction, as determined from offsetting well data. To better define sections with limited, poor or missing log data (because of difficult hole conditions), drilling data, logging while drilling (LWD) gamma ray data, openhole conventional and dipole sonic logs, along with prior 1D stress data were used with a machine learning model to improve stress profiling and reservoir characterization. Next, perforations were shot 0 and 180° phased along the wellbore and initial fluid viscosity was increased to better align the hydraulic fracture and reduce NWBPL, respectively. Finally, diagnostic fracture injection tests (DFIT) were performed in sections of varying moduli below and in the zone of interest in order to verify the horizontal strains and calibrate the final 1D stress profile prior to stimulating both wells. The improved well and perforation alignment to the maximum horizontal stress direction has improved reservoir connection, lowered NWBPL in some cases, and in some cases improved fracture containment. Decreasing injection rates and minimizing perforated intervals has improved targeting of desired intervals; however, overall fracture widths remain low and continue to be sensitive to proppant sizing and concentrations with several screen outs experienced. This experimentation has resulted in short-term production improvements in the wells using 4- and 3-stage treatments relative to the offsetting vertical well where a 5-stage treatment was executed.
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