Characteristics and Effect on Productivity of the Sandstone and Fractures in Ultra-deep and Fractured Tight Sandstone Gas Reservoirs:A Case Study of KS2 Gasfield in Kuqa Depression,Tarim Basin

doi:10.19657/j.geoscience.1000-8527.2020.097

Abstract

Abstract:

Tectonic fractures are widespread in the KS2 gasfield and the fracture development characteristics differ with the structure locations. The single-well production in this area is controlled by the features of the sandstone and fractures. In this study, we determined the lithological characteristics, sand combination features and properties such as the degree, filling and occurrence of the fractures in the reservoir through analyzing the cores, slices, SEM and well-log data. Besides, we analyzed the relations between the well production and aforementioned sand and fracture features. The results show that the well production is affected by many factors of the property of the sand and fractures: wells located in the areas controlled by both faults and anticline have higher production, as indicated by routine test or acidification test; fractures with single direction are usually widespread in the anticline-controlled areas, and the wells there need to be tested by artificial hydraulic fracturing to obtain higher yield; fractures are poorly-developed in areas such as limbs and axis of the anticlines, and the wells there usually have low productivity.

Key words: tight sandstone gas reservoir, sandstone, fractures, productivity, developmental characteristics, Kuqa Depression

CLC Number:

TE122.2

FU Xiaotao, WANG Yimin, SHAO Jianbo, ZHU Songbai, WANG Yong, NIE Yanbo, WANG Bin, DUAN Qiqi. Characteristics and Effect on Productivity of the Sandstone and Fractures in Ultra-deep and Fractured Tight Sandstone Gas Reservoirs:A Case Study of KS2 Gasfield in Kuqa Depression,Tarim Basin[J]. Geoscience, 2021, 35(02): 326-337.

Figures/Tables 14

Fig.1 Structural location and stratigraphic map of the KS2 gasfield in the Kuqa Depression

Fig.2 Histogram of porosity and permeability of the core samples in KS2 gas field

Fig.3 Microscopic features of the reservoir in petrographic thin-sections and SEM images in the KS2 gasfield

Table 1 Integrated features of the sand-bodies in the KS2 gasfield

类型	砂体组合	厚度/ m	岩性	物性 ( $K / 10 - 3 μ m 2 Φ / %$ )	测井曲线 (GR,R)	沉积微相
Ⅰ	厚层水下分流河道叠置砂体	10~20	中砂岩、细砂岩	$0.03 ~ 0.12 4 ~ 12$	箱形,相对光滑、平整,或低幅度齿化	主河道
Ⅱ	中-厚层水下分流河道叠置砂体	5~15	含泥砾细砂岩、细砂岩、中砂岩	$0.01 ~ 0.1 4 ~ 9$	齿化箱形	主河道,分支河道
Ⅲ	水下分流河道与河口坝叠置砂体	2~10	泥质粉砂岩、粉砂岩、细砂岩	$0.01 ~ 0.08 1 ~ 6$	漏斗形+钟形,GR下高上低,R下低上高	水下次级分流河道与河口坝叠置
Ⅳ	单套水下分流河道小规模砂体	1~8	粉砂岩、泥质粉砂岩	$0.01 ~ 0.8 2 ~ 8$	宽指形,高幅度齿化	分支河道或主河道侧缘远端

Table 1 Integrated features of the sand-bodies in the KS2 gasfield

类型	砂体组合	厚度/ m	岩性	物性 ( $K / 10 - 3 μ m 2 Φ / %$ )	测井曲线 (GR,R)	沉积微相
Ⅰ	厚层水下分流河道叠置砂体	10~20	中砂岩、细砂岩	$0.03 ~ 0.12 4 ~ 12$	箱形,相对光滑、平整,或低幅度齿化	主河道
Ⅱ	中-厚层水下分流河道叠置砂体	5~15	含泥砾细砂岩、细砂岩、中砂岩	$0.01 ~ 0.1 4 ~ 9$	齿化箱形	主河道,分支河道
Ⅲ	水下分流河道与河口坝叠置砂体	2~10	泥质粉砂岩、粉砂岩、细砂岩	$0.01 ~ 0.08 1 ~ 6$	漏斗形+钟形,GR下高上低,R下低上高	水下次级分流河道与河口坝叠置
Ⅳ	单套水下分流河道小规模砂体	1~8	粉砂岩、泥质粉砂岩	$0.01 ~ 0.8 2 ~ 8$	宽指形,高幅度齿化	分支河道或主河道侧缘远端

Fig.4 Distribution of the types of sand-bodies in study area

Fig.5 Histogram of ratios of four types of sand-bodies in study area

Fig.6 Histogram of structural fractures in the KS2 gasfield

Fig.7 Thin-section microscopic features of drill-cores and slices from the KS2 gasfield

Fig.8 Histogram of structural fracture aperture and filling percentage in the study area

Fig. 9 Distribution map showing the fracture oienation of the KS2 gasield

Fig.10 Distribution map showing the fracture linear density of the KS2 gasfeld

Fig.11 Fracture distribution model of the faulted anticline (modified from ref [15])

Fig.12 Relationship between single well production and sand types & linear density of fractures in KS 2 area

Fig.13 Map showing the single well production in different ways in KS 2 gas field

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