Journal of Petroleum & Environmental Biotechnology

Reservoir properties of light tight oil bearing shelly limestone and corresponding EUR in the central Sichuan Basin, China

5^th World Congress on Petrochemistry and Chemical Engineering

December 05-07, 2016 Phoenix, USA

Shaoyong Wang

Research Institute of Petroleum Exploration and Development- PetroChina, China

Posters & Accepted Abstracts: J Pet Environ Biotechnol

Abstract:

The EURs and decline types of 120 vertical wells spread across the central Sichuan Basin and targeting the Daâ??anzhai formation were calculated by fitting monthly production data. Core observations, thin section analysis and scanning electron microscopy (SEM) were used to determine the storage space type and oil-bearing properties of the shelly limestone. The aim of this study was to determine the relationship between the estimated ultimate recovery (EUR) and geological factors. The results showed that all the matrix pores and fractures in the shelly limestone were oil-bearing. The type of reservoir space structure in the Daâ??anzhai formation can be classified as fracture-cave, fracture-pore and fracture. Vertical wells targeting the shelly limestone with these reservoir space structures might have respective production decline types corresponding to exponential decline, logarithmic decline and powerlaw exponential decline. Wells with each empirical decline type had diminishing EURs of 86.1, 39.3 and 5.9 MSTB (P50). Both the fractional thickness of the limestone occupied by the fracture and the ratio of the cave shelly limestone in the reservoir were positively and linearly related to the EUR. The proportions of megaports, macroports, mesoports, microports, and nanoports in the shelly limestone were 1.6%, 3.7%, 18.1%, 27.8%, and 48.8%, respectively, and the corresponding EUR range of each pore size class tended to be above 294 MSTB, 110 to 294 MSTB, 37 to 110 MSTB, 4 to 37 MSTB, and below 4 MSTB. The results indicated that nearly 77% of the vertical wells targeting the Daâ??anzhai formation may have been uneconomical if stimulation was not conducted.

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