地学前缘 ›› 2024, Vol. 31 ›› Issue (5): 139-155.DOI: 10.13745/j.esf.sf.2023.6.21

• 致密砂岩储层裂缝研究 • 上一篇    下一篇

扇三角洲前缘非常规致密油储层裂缝发育模式:以泌阳凹陷东南部古近系核三段为例

尹帅1(), 张子阳1, 张星星2, 王景辰3, 胡伟4, 丁文龙5, 李虎6   

  1. 1.西安石油大学 地球科学与工程学院, 陕西 西安 710065
    2.中国石油青海油田公司 采气二厂, 甘肃 敦煌 736202
    3.中国石油塔里木油田公司 监督中心, 新疆 库尔勒 841000
    4.中国石油塔里木油田公司 勘探开发研究院, 新疆 库尔勒 841000
    5.中国地质大学(北京) 能源学院, 北京 100083
    6.西南石油大学 地球科学与技术学院, 四川 成都 610500
  • 收稿日期:2023-11-15 修回日期:2024-04-11 出版日期:2024-09-25 发布日期:2024-10-11
  • 作者简介:尹帅(1989—),男,博士,副教授,从事深部非常规油气地质理论与应用技术、储层地质力学、储层测井评价及岩石力学基础实验研究工作。E-mail: speedysys@163.com
  • 基金资助:
    国家自然科学基金项目(42302167);陕西省自然科学基础研究计划项目(2023-JC-QN-0355);西安石油大学研究生创新基金项目(YCX2411002)

Fracture development mode in fan delta front unconventional tight oil reservoirs: A case study of Paleogene He-3 in southeastern Biyang Depression

YIN Shuai1(), ZHANG Ziyang1, ZHANG Xingxing2, WANG Jingchen3, HU Wei4, DING Wenlong5, LI Hu6   

  1. 1. School of Earth Science and Engineering, Xi’an Shiyou University, Xi’an 710065, China
    2. No.2 Gas Production Plant, Qinghai Oilfield Company of PetroChina, Dunhuang 736202, China
    3. Engineering Supervision Center, Tarim Oilfield Company, PetroChina, Korla 841000, China
    4. Research Institute of Exploration and Development, Tarim Oilfield Company, PetroChina, Korla 841000, China
    5. School of Energy Resources, China University of Geosciences (Beijing), Beijing 100083, China
    6. School of Geoscience and Technology, Southwest Petroleum University, Chengdu 610500, China
  • Received:2023-11-15 Revised:2024-04-11 Online:2024-09-25 Published:2024-10-11

摘要:

泌阳凹陷东南部位于古湖盆短轴陡坡一侧,发育牵引流驱动的扇三角洲前缘复杂沉积体系,不同类型砂体中裂缝的定量刻画对非常规致密油勘探开发具有重要指导作用。该地区古近系核桃园组三段属典型的“凹中隆”背景下的扇三角洲前缘沉积,目前对于该类沉积及构造背景下的天然裂缝发育规律的认识仍存在不足。本文以该地区核三段从Ⅱ到Ⅵ砂组非常规陆相致密油储层为例,利用大量岩心、物性、常规、成像测井资料和数值模拟方法,系统研究了致密砂岩储层裂缝特征及分布规律,提出了该地区扇三角洲前缘非常规致密油储层裂缝发育模式。研究结果表明,岩性、砂体厚度、沉积作用和构造均对致密砂岩储层裂缝分布有显著的控制作用。薄层单砂体或其复合砂体中更容易发育裂缝,当单砂体厚度大于6 m时,砂体中裂缝通常相对欠发育。裂缝主要发育于水下分流河道前缘、侧向加积河道单翼、河口坝和远砂坝中。将河道类型划分为均质河道和非均质河道。侧向快速堆积形成的非对称型非均质河道中砂体叠置厚度较大,可超过18 m,裂缝较为发育;对于均质河道前缘,即靠近扇三角洲前缘河口坝微相区域,其在垂向上通常发育于靠近河口坝顶部的沉积序列中,代表较强的水动力条件,裂缝也较为发育。裂缝与油气聚集有密切的关系,工区核三段裂缝主要形成于新近系坳陷期。通过DFN离散裂缝模拟,恢复了主力小层裂缝三维空间展布。结果显示,核三段主要发育E-W和NE向两组共轭裂缝,且局部以发育其中一组为主,这些裂缝多平行或垂直于隆起构造痕线分布。天然裂缝在背斜低部位和翼部相比顶部更为发育。此外,多条共轭剪切缝相交或同走向一侧单翼裂缝相连接可形成“裂缝嵌合带”,其可能为压驱过程中长距离水窜产生的直接诱因,因而在后期压驱中要规避“裂缝嵌合带”。

关键词: 泌阳凹陷, 非常规致密油储层, 沉积, 构造, 裂缝发育规律

Abstract:

The southeastern Biyang Depression is located on the steep slope of the short axis of a paleolake basin, with a complex sedimentary system of fan delta front driven by traction flow in the Paleogene. Quantitative characterization of fractures in different fabric sand bodies plays an important role in guiding unconventional tight oil exploration and development. The third member of the Paleogene Hetaoyuan Formation (He-3) in the southeastern Biyang Depression belongs to fan delta front deposit under an “uplift in depression” setting, and natural fractures have a direct influence on the adjustment of infill well pattern and the scientific formulation of enhanced oil recovery scheme. In this paper, taking the shallow middle-layer (Ⅱ-Ⅵ oil formation) continental tight sandstones of He-3 as an example, the fracture characteristics and distribution law are systematically studied using core, physical property, conventional and image logging data and numerical simulation method; the pattern of fracture development in unconventional tight oil reservoirs at the front edge of the fan delta of the study area is proposed. Lithology, sand body thickness, sedimentation and structure have significant control on fracture distribution in shallow, middle-layer tight sandstone reservoirs. Fractures are more likely to develop in single or composite thin sand bodies. Usually fractures are relatively underdeveloped when the single sand body thickness is greater than 6 m. Shallow, middle-layer fractures are mainly developed at the front of underwater distributary channel, single wing of lateral accretion channel, estuary bar and far sand bar. The river channel types are divided into homogeneous and heterogeneous. The superimposed thickness is larger in asymmetrical heterogeneous channels formed by rapid lateral accumulation, which can exceed 18 m, and the fractures are relatively developed. The homogeneous channel front, that is, the microfacies area near the fan delta front of the estuary bar, usually develops vertically in the sedimentary sequence near the top of the estuary bar, indicating strong hydrodynamic conditions and relatively developed fractures. Fractures are closely related to oil and gas accumulation. Fractures in He-3 are mainly formed in the Neogene depression period. The three-dimensional distribution of the main small-layer fractures is restored through DFN simulation. The results show that two groups of conjugate fractures are mainly developed in the E-W and NE directions, and one group is mainly developed locally. These fractures are mostly distributed parallel or perpendicular to the uplift structure. Natural fractures are more developed in the lower parts and wings of an anticline compared to its crest. In addition, the intersection of multiple conjugated fractures can form a “fracture chimeric zone,” which may be the direct cause of long-distance water channeling in the pressure flooding process, so the “fracture chimeric zone” should be avoided in the flooding process.

Key words: Biyang Depression, unconventional tight oil reservoir, deposition, structure, fracture development law

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