Fig 7 - uploaded by Denis Marchal
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Open and semi-open fracture orientations and breakout directions. In general, the wells display fracture orientations and breakout directions very similar to those of well F, in the entire field.
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Context 1
... analysis of the direction of the open to semi-open fractures shows a dominant NW-SE orientation in most of the wells (Fig.7). Different orientation of the fractures in some wells can be linked directly to the influence of the associated fault. ...
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Citations
Integrated geological-geophysical methods have been used to depict the geometric characteristics and kinematic evolution of the Shunbei 5 (SB5) and adjacent Shunbei1 (SB1) strike-slip faults in the central Tarim Basin, China. Geometric evidence for strike-slip faulting includes the occurrence of positive and negative flower structures in stepover zones, oblique secondary splay faults, en echelon folds, and adjacent secondary faults. The multi-humped along-strike and along-dip displacement variations of the SB5 fault provide insights into the initial segmentation, interaction and polycyclic growth of the fault zones both in plan and section views: The SB5 fault initiated as an apparent “X-type” conjugate pure shear fault system in the north and a simple shear fault system in the south respectively. At depth (mainly in Cambrian to Middle Ordovician rocks), the northern and southern parts of the SB5 fault exhibit a typical dextral strike-slip architecture consisting of multiple fault segments connected via transpressional push-up or transtensional pull-apart stepovers or bends. The southern part has a linear, narrow sinistral ridge system. At shallower depths (in Upper Ordovician to Middle Devonian rocks), the lower subvertical faults propagated upwards as en echelon normal faults in the north, and as a two-phase, partitioned system consisting of boundary grabens and en echelon normal faults that dissected the early-formed border grabens in the south. With progressive deformation, the northern and southern parts of the SB5 fault reactivated and transferred into one large, sinistral fault in Upper Devonian to Permian rocks. Four major tectonic phases matching the kinematic evolutions of regional fault systems and uplifts in the study region, have also been recognized in the Middle Ordovician to Cretaceous. The pull-apart stepover and single fault zones developed in Middle Ordovician rocks are favorable fracture-related reservoirs.
The fault system in the 3D seismic region of northern Shun 8 block (Tarim Basin) is mainly composed of NNW-SSE and NE-SW orientation faults. The No.7 fault zone in the NNW-SSE orientation extends linearly on the plane. It partially exhibits segmentation characteristics. According to the fault plane spread feature of the partial extensional section, the No.7 fault zone is the left-order left-lateral strike-slip fault. The SHB7 well on the No. 7 fault zone was drilled to the vicinity of the extensional section. The successive strike-slip stress field generated multiple sets of fractures in different orientations. The integration of 3D seismic, image logs and production logging analysis reveals the clustering of productive fractures around the fault zone. These open to semi-open production fractures are inconsistent with the tectonic stress state of the present day acting in this part of the Tarim Basin, indicating that the present-day tectonic play no role in production rate. The Build-up tests show three main types of responses: (1) A-type displays a radial flow and there is no test boundary for a longer period of time, (2) B-type displaying a short radial flow period followed by bilinear flow and (3) C-type is only related to bilinear flow. These three flow responses are linked with structural models of fault associated production fractures. Analysis of geological and production data indicates that the spatial distribution of productive fracture zones is primarily controlled by open fractures. A better understanding of the production system allows us to optimize the drilling location and select the appropriate well production zonees.
