Characteristics of Fractures and Dissolved Vugs of LWM Formation Gas Reservoir in Moxi Block and Its Influence on Gas Well Productivity

Abstract

The Longwangmiao Formation gas reservoir in Moxi block is a lithologic-structural gas reservoir with large gas-bearing area and low structural amplitude. There is a risk of rapid water invasion in the gas production due to strong heterogeneity of fractures and dissolved vugs. Therefore, to clarify the characteristics of reservoir fractures and vugs and its effect on gas well productivity, is of great significance to fine characterization of water invasion channels, optimization of development technology policy, and improvement of gas reservoir development effect. On the basis of detailed description of core fracture and interpretation of imaging logging, this paper makes a comprehensive analysis of geological and dynamic data. The results show that: Firstly, Reservoir dissolution pores and vugs are well developed, but their spatial distribution is strong heterogeneous. They are concentrated in the middle part of Longwangmiao Formation vertically and distributed in two main grain shoals horizontally. The main grain shoals are mostly composed of single shoal with length of less than 20 m and width of less than 10 m. The single shoal mainly distribute in NE-SW direction, with a maximum length of 190 m and a width of about 50 m. Secondly, there are three kinds of natural fractures, which are mainly high-angle structural fractures. Among them, the unfilled high-angle fractures are large in scale and penetrate the Longwangmiao Formation strata. These high-angle structural fractures are widespread developed in the whole area, most of them developed in four relative development zones. Thirdly, influenced by the development of reservoir micro-fractures, the development scale of high-quality reservoirs (Reservoir with millimeter sized dissolved vugs and solution pores) is the main factor determining gas well productivity; a large number of high-angle structural fractures can effectively connect the interior of gas reservoirs, and greatly increase reservoir permeability by 1–2 orders of magnitude.

Copyright 2019, IFEDC Organizing Committee.

This paper was prepared for presentation at the 2019 International Field Exploration and Development Conference in **’an, China, 16–18 October, 2019.

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