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European Journal of Applied Sciences – Vol. 11, No. 1
Publication Date: January 25, 2023
DOI:10.14738/aivp.111.13812.
Wang, H., Dan, G., Zhang, J., Li, X., Lu, Z., Liu, Y., Zhang, L. & Xu, J. (2023). Control of Ultra-deep Strike-slip Fault Reservoir and
Hydrocarbon Migration: A Case Study of HD Block in Tarim Basin. European Journal of Applied Sciences, 11(1). 134-146.
.
Services for Science and Education – United Kingdom
Control of Ultra-deep Strike-slip Fault Reservoir and
Hydrocarbon Migration: A Case Study of HD Block in Tarim Basin
Huailong Wang
China National Petroleum Corporation, PetroChina Tarim Oilfield Company,
Korla Xinjiang Province 841000, China
Guangjian Dan
China National Petroleum Corporation, Bureau of Geophysical Prospecting Inc.,
Zhuozhou Heibei Province 072750, China
Jie Zhang
China National Petroleum Corporation, PetroChina Tarim Oilfield Company,
Korla Xinjiang Province 841000, China
Xiangwen Li
China National Petroleum Corporation, Bureau of Geophysical Prospecting Inc.,
Zhuozhou Heibei Province 072750, China
Zhongyuan Lu
China National Petroleum Corporation, PetroChina Tarim Oilfield Company,
Korla Xinjiang Province 841000, China
Yonglei Liu
China National Petroleum Corporation, Bureau of Geophysical Prospecting Inc.,
Zhuozhou Heibei Province 072750, China
Lei Zhang
China National Petroleum Corporation, Bureau of Geophysical Prospecting Inc.,
Zhuozhou Heibei Province 072750, China
Jianyang Xu
China National Petroleum Corporation, Bureau of Geophysical Prospecting Inc.,
Zhuozhou Heibei Province 072750, China
ABSTRACT
The reservoirs in the HD area, Tarim Basin, are strictly controlled by the
distribution of faults. On the basis of the latest high-precision three-dimensional
seismic data as well as an understanding of the strike-slip fault theoretical model,
the structural styles, assembly of major and secondary faults, movement history
and relationship between fault activity and hydrocarbon accumulation are
determined in the forms of seismic related section illustration and planar
appearance. The study shows that the NE-oriented strike-slip faults of the
Ordovician was activated from the middle Caledonian period and that the northern
part displayed stronger activity than the southern part. This fault belt is the major
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135
Wang, H., Dan, G., Zhang, J., Li, X., Lu, Z., Liu, Y., Zhang, L. & Xu, J. (2023). Control of Ultra-deep Strike-slip Fault Reservoir and Hydrocarbon Migration:
A Case Study of HD Block in Tarim Basin. European Journal of Applied Sciences, 11(1). 134-146.
URL: http://dx.doi.org/10.14738/aivp.111.13812
fault in the study area and serves as the first-order oil source fault. The south-north
thrust fault started to move in the early Hercynian and intersected with the main
strike-slip faults. Considering the distribution of thrust, this fault acts as the
secondary oil source fault. The hydrocarbons in the Ordovician reservoir are
predominantly transferred by vertical in situ migration through SSFs and thrust
faults. These faults cut deep into the source layer and played a major role in
hydrocarbon migration. The NW-trending secondary SSF in the central part of the
study area was formed in the middle and late Caledonian. The fault mainly controls
the distribution of the reservoir and contributes little to hydrocarbon transfer.
Therefore, the hydrocarbon potential around this fault is unfavorable.
Keywords: Hydrocarbon accumulation, Strike-slip fault, Fault characteristics, Oil-sourced
fault, HD area, Tarim Basin.
INTRODUCTION
The platform of the Tarim Basin develops many Ordovician strike-slip faults (SSFs). The early- stage exploration of the Ordovician carbonate reservoir focused on the Lungu buried hill karst
zone and the reef in the eastern Tarim Basin. With the continuous advancement of oil and gas
exploration, the development concentrated more on the fault-controlled karst zone and
obtained high-yield industrial oil and gas in the SSF zones in the Tabei and Tazhong areas.
Currently, the Ordovician carbonate SSF zones are the main battlefield of oil and gas exploration
in the Tarim Basin.
The Ordovician SSFs in the Tabei and Tazhong areas, especially their tectonic styles, evolution,
formation mechanism, and storage control mode, have drawn more attention from scholars in
recent years [1-7]. However, the relationship varies between the characteristics of the
Ordovician SSFs and hydrocarbon accumulation in each block. Taking the HD area as an
example, how SSFs affect hydrocarbon accumulation and reserves is complicated because it
experiences multiple tectonic stresses and develops both strike-slip and thrust faults. The
relationship between the characteristics of SSFs and reservoir formation in this block has not
yet been clarified. In the HD block, most wells targeting large fractured-vuggy bodies in the
early exploration stage are inefficient or ineffective. In addition, high-yield and inefficient wells
simultaneously present on the same SSF zone confirm that it contains segmental enrichment.
There is no relevant literature related to the relationship between the Ordovician SSFs and the
hydrocarbon accumulation in this area. Therefore, it is essential to conduct a systematic review
to improve the drilling success rate.
Based on the latest high-precision three-dimensional seismic data and the theoretical model of
SSFs, this paper discusses its structural style, the relationship between primary and secondary
faults, active periods, and its relationship with hydrocarbon accumulation in the HD area from
the profile style and plane distribution characteristics. This paper confirms that SSFs are the
main controlling factor in hydrocarbon accumulation by analyzing the success and failure
reasons of previous wells. It also defines the oil and gas enrichment in different sections of SSFs
by evaluating the source connecting features. Most importantly, it provides a new conception
for oil and gas development in the HD area.
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European Journal of Applied Sciences (EJAS) Vol. 11, Issue 1, January-2023
Services for Science and Education – United Kingdom
GEOLOGICAL BACKGROUND
The HD Oilfield is located in the southern slope belt of the Lunnan Low Uplift in the Tabei Uplift
(Figure 1). It is adjacent to the Manjiaer depression to the southeast and receives most of the
hydrocarbons generated in the Sag [8]. The Ordovician strata in the HD Oilfield appear as a
nose-like structure sloping to the south.
The 3D full coverage area of the HD area is 690 km2. It is the prestack depth migration data
reprocessed in recent years. The seismic data have a high signal-to-noise ratio and can satisfy
the requirement of the fine description of faults and reservoirs.
Figure 1. Structural map of the top Ordovician limestone in the Tabei area.
The Lunnan Lower Uplift of the Tabei Uplift is a large palaeo-uplift developed on the pre-Sinian
metamorphic rock and undergoes multiphase tectonic movement and deformation
superimposition [9]. It has mainly gone through six stages of evolution. This first stage was the
early Caledonian, which was under the extension of the entire Tarim Craton. The second stage
is the middle and late Caledonian period, in which the north passive continental margin recoils,
and the stress to the basin changes from extension to compression, which causes the formation
of the Lunnan low bulge. The third period was the early Hercynian, which was uplifted by
regional compression to form a large northeast spreading nose protruding to the southwest.
The late Hercynian period followed, when the entire area was uplifted and exposed to
denudation. The last stage was the Indosinian-Yanshanian period. The tectonic movement in
this area was relatively weak, mainly manifested in the overall up-and-down period, and the
Tabei uplift and the Lunnan low uplift finally took shape. HD is located on the southern slope of
the Lunnan Lower Uplift.
The Ordovician strata are a carbonate platform in the Tabei area. It experiences multistage
unconformity exposure and develops high-energy beach bodies and large-scale fracture-cavity
karst reservoirs. The Tabei area has high-quality source rocks under Cambrian strata, and the
HD Oilfield is immediately above the hydrocarbon generating center [8]. Under the influence of
SSFs, Ordovician carbonate fractured-vuggy reservoirs form along faults, and hydrocarbons
vertically migrate and charge through them. Therefore, faults are key to karst oil and gas
reservoirs [10-11].
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137
Wang, H., Dan, G., Zhang, J., Li, X., Lu, Z., Liu, Y., Zhang, L. & Xu, J. (2023). Control of Ultra-deep Strike-slip Fault Reservoir and Hydrocarbon Migration:
A Case Study of HD Block in Tarim Basin. European Journal of Applied Sciences, 11(1). 134-146.
URL: http://dx.doi.org/10.14738/aivp.111.13812
IDENTIFICATION AND DESCRIPTION OF SSFS
Faults identification is a process of characterizing the fracture based on its features on the
seismic profile and the discontinuity attributes on the surface slice. The discontinuity attribute
describes faults based on physical quantities to characterize the amplitude energy or structural
difference of the adjacent trace of seismic data [12-13]. Conventional discontinuity attributes
include coherence, curvature, and ant-body [14]. They are all data-driven attributes, so the
prediction accuracy relies on the quality of seismic data. HD 3D acquisition was carried out in
2012. The N–S acquisition direction is nearly parallel to the main SSF and is not conducive to
fault imaging. In addition, the Ordovician limestone in the southern part of the HD area is buried
more than 7000 meters, and the main frequency of the target layer is less than 20 Hz, resulting
in a low signal-to-noise ratio and resolution. Coherence attributes have difficulty describing
fault distributions: fault imaging is not clear, especially for small faults. The fault reflection on
the seismic section is indistinct and increases the difficulty of fracture interpretation [15].
To improve the clarity of the description of faults in seismic data, we conducted poststack
multiple filter interpretative processing on the original seismic data (Figure 2a). First, the
seismic data are filtered by the frequency domain, and the middle- to high-frequency seismic
data that can identify small fractures are chosen for structure-oriented filtering (Figure 2b).
Structure-oriented filtering can increase the continuity of the seismic event axis and the lateral
resolution at the endpoint [16-17]. which can further improve the sharpness of the fault. After
this, the continuous and discontinuous features are more prominent, the fault points are
crisper, and the imaging of SSFs is clearer. On this basis, the coherence attribute of the top
surface of the HD Ordovician limestone reflects more details compared with the previous one
obtained from original seismic data (Figure 2c, 2d). This effectively solves the problem of
inefficiently identifying small strike-slip fractures in this area.
We reorganized the HD Ordovician fault system using this method and explained 228 faults
with a total length of 74 km (Figure 3a). The faults are well developed in the northern part of
the research area and decrease southward, which indicates that tectonic activity and
compressional stress are stronger in the northern area. There are four large-scale SSF zones,
named HD251, HD29-1, HD30, and HD26. Except for HD26, which is northwest-trending, the
others are mainly NNS. The main SSFs are high-angle faults (Figure 3b) that cut through the
Cambrian base to the Ordovian Yijianfang (TO2y) Formation. They are the major channel for
upward hydrocarbon migration. There is a large thrust fault zone named HD27, which cuts
upward to the Carboniferous and downward to the middle Cambrian gypsum salt rock (Figure
3b). A large number of small NW-trending SSFs have developed between the HD 30 and HD29-
1 SSFs, which only developed in the Ordovician Yingshan (TO12y) Formation and TO2y
Formation (Figure 3b).
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European Journal of Applied Sciences (EJAS) Vol. 11, Issue 1, January-2023
Services for Science and Education – United Kingdom
Figure 2. Coherence slices of the top surface of Ordovician limestone in the HD area.
(a) (b)
Figure 3. The top surface fracture system and EW seismic profile of the Ordovician TO2y
Formation in the HD area. a. The top surface fracture system of the Ordovician Yijianfang
formation in the HD area. b. EW seismic profile.
Fault Formation Mechanism and Period Analysis
The SSFs are caused by torsional stress or shear stress in the formation and have a relative
horizontal movement [18]. The Tabei Uplift mainly develops large-scale northeast and
northwest SSFs (Figure 4). The stress mechanism of SSFs in the northern part came from
passive continental margin reactions, which were affected by the Kunlun and Aerjin orogenic
activities in the mid-late Caledonian period [19-20], and the stress of the interior basin changed