石油与天然气地质 ›› 2021, Vol. 42 ›› Issue (4): 963-972.doi: 10.11743/ogg20210416

• 方法技术 • 上一篇    下一篇

四川盆地川西坳陷上三叠统须家河组储层各向异性地应力评价方法

张金才1(), 范鑫2,*(), 黄志文2, 刘忠群2, 亓原昌1   

  1. 1. 中国石化 休斯顿研究开发中心, 美国 休斯顿 TX 77056
    2. 中国石化 石油勘探开发研究院, 北京 100083
  • 收稿日期:2020-10-19 出版日期:2021-08-28 发布日期:2021-08-27
  • 通讯作者: 范鑫 E-mail:jzhang.sthc@sinopec.com;fanxin.syky@sinopec.com
  • 第一作者简介:张金才(1963-), 男, 博士、地质与石油物理顾问, 地质力学、岩石力学与石油工程。E-mail: jzhang.sthc@sinopec.com
  • 基金项目:
    中国石化科技部项目(P18089-5);中国石化科技部项目(P20056-3)

Assessment of anisotropic in-situ stressses in the Upper Triassic Xujiahe Formation reservoirs in Western Sichuan Depression of the Sichuan Basin

Jincai Zhang1(), Xin Fan2,*(), Zhiwen Huang2, Zhongqun Liu2, Yuanchang Qi1   

  1. 1. Sinopec Tech Houston, Houston, Texas 77056, USA
    2. Petroleum Exploration and Production Research Institute, SINOPEC, Beijing 100083, China
  • Received:2020-10-19 Online:2021-08-28 Published:2021-08-27
  • Contact: Xin Fan E-mail:jzhang.sthc@sinopec.com;fanxin.syky@sinopec.com

摘要:

尽管四川盆地川西坳陷上三叠统须家河组砂岩是非常致密的气藏,但是其中一些储层天然裂缝发育,尤其是须二段的优质储层,垂直裂缝或高角度裂缝发育。这导致了岩层和水平主应力的各向异性。对于这类储层如果采用常规的各向同性地应力评价方法,则会高估岩层的实际水平主应力。根据钻井中的溢流、井涌和测试压裂,以及井壁崩落等数据研究了这类储层地应力的新的评价方法,得到了新场气田和合兴场气田的地层压力与地应力实测结果。这些结果表明岩层的天然裂缝对地应力有较大的影响。采用各向异性理论建立了须家河组储层地应力的VTI和HTI模型。含天然裂缝储层的实测数据表明,随着裂缝密度、裂缝倾角和裂缝指示因子的增大,水平主应力和破裂压力减小,这与HTI模型相吻合。结合各向异性模型与天然裂缝、水平主应力和破裂压力的实测数据,得出了适合于须家河组储层特点的地应力预测公式及其对压裂影响的评价方法。

关键词: 裂隙岩层, 水平主应力, 地应力, 各向异性, 水力压裂, 须家河组, 三叠系, 四川盆地

Abstract:

The Triassic Xujiahe Formation sandstones in the western Sichuan Depression are tight gas reservoirs, some of which contain natural fractures, particularly for the gas-rich reservoir in the 2nd member of the Xujiahe Formation (hereafter referred to as Xu 2 Member) with well-developed vertical or high dip angle fractures. Anisotropies of both rocks and horizontal principal stresses are thereby resulted. To calculate in-situ stresses in the naturally fractured formations using conventional methods obtained in the isotropic formation may overestimate the horizontal principal stress. New assessment methods of in-situ stresses in the anisotropic formations are studied in this paper. The in-situ stressess and formation pressures in the Xinchang and Hexinchang gas fields are obtained based on measured data from wellbore influxes, kicks, mini-frac tests and wellbore breakouts.The measured results indicate that natural fractures have a great impact on the in-situ stresses. The theory of anisotropy is applied to establish the in-situ stress models of VTI and HTI for the Xujiahe Formation reservoirs. The measured data in the formations with natural fractures reveal that the horizontal principal stress and formation breakdown pressure decrease as the natural fracture density, dip angle and intensity index increase. This is consistent to the derived HTI model. The assessment methods for in-situ stresses and their impact on hydraulic fracturing are proposed for the Xujiahe Formation reservoirs based on the anisotropic model and the measured data of natural fractures, horizontal stresses and breakdown pressures.

Key words: fissured formation, horizontal principal stress, in-situ stress, anisotropy, hydraulic fracturing, Xujiahe Formation, Triassic, Sichuan Basin

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