3D Modeling of Fracture-Cave Reservoir from a Strike-Slip Fault-Controlled Carbonate Oilfield in Northwestern China

Abstract

A giant strike-slip fault-controlled Fuman Oilfield has been found in the Ordovician fractured carbonates of the Tarim Basin. However, conventional seismic methods are hardly able to distinguish the fractured reservoir and its connectivity in the ultra-depth (>7000 m) carbonate fault zones. We propose thin-likelihood and tensor-thickness process methods to describe the fracture network and large cave reservoir, respectively. Together with the two methods for 3D visualization of fracture-cave reservoirs, we had an application in the ultra-deep well deployment in Fuman Oilfield. The results show that the fracture network and cave reservoir can be 3D-imaged more clearly than conventional methods. The fracture network and cave reservoir show distinct segmentation by the fault assemblage in Fuman Oilfield. Furthermore, 3D modeling is favorable for the reservoir connectivity description along the carbonate fault zones. There are three distinct reservoir models: fault core-, fault damage zone- and overlap zone-controlling fractured reservoirs along the fault zones. This revealed variable fractured reservoirs that are related to fault maturity and segmentation. The method has been widely used in fracture-cave reservoir description and subsequent well optimization, suggesting a favorable method for economic oil exploitation in the ultra-depth reservoirs. This case study is not only useful for the complicated reservoir 3D description and modeling but also helpful for well employment to provide support for the target evaluation and optimization in ultra-depth fractured reservoirs.

The Advances and Challenges of the Ediacaran Fractured Reservoir Development in the Central Sichuan Basin, China

“…Generally, it is hard to describe the small-scale fracture and fractured reservoirs in the deep subsurface [31][32][33]. Owing to the fracture and fractured reservoirs often occurred…”

“…Generally, it is hard to describe the small-scale fracture and fractured reservoirs in the deep subsurface [31][32][33]. Owing to the fracture and fractured reservoirs often occurred in the fault damage zone, we use seismic illumination attribute to constrain the envelope of the fault damage zone and the fracture-cave reservoirs.…”

“…The seismic illumination process is based on the analysis parameters of illumination energy that are favorable for improving the imaging accuracy of seismic data in complex structures (the method based on references [34,35]). In addition, we use attribute fusion by structural tensor attribute (similar method to reference [33]) to improve the images of the fault damage zone and the fractured reservoirs. Using well calibration, the fusion of these attributes was performed to distinguish the fracture network and fractured reservoirs from the surrounding rocks.…”

“…Due to the tight matrix reservoirs in the deep carbonates, fractured reservoirs are of significant importance in hydrocarbon exploitation in heterogeneous reservoirs [31][32][33]. The fracture network can enhance the permeability by 1-3 orders of magnitude and the fracture-related dissolution porosity by more than 20% in the deep tight reservoirs.…”

“…In this way, the "sweet spot" of fractured reservoirs is the favorable target for economic production along the strike-slip fault damage zone. The fractured reservoir has been studied by geological, geophysical and engineering methods, of which the seismic technology plays an important role in the reservoir description [32,33,[36][37][38]. Owing to the intense heterogeneity of fractured reservoirs and low-resolution seismic data, there is still a big challenge in the description of fractured reservoirs in the deep subsurface.…”