Theoretical basis and prospect of coal measure unconventional natural gas co-production

Theoretical basis and prospect of coal measure unconventional natural gas co-production

Natural gas

Methane

Hydrocarbons

Process control

Gas industry

Petroleum reservoir engineering

Boreholes

Oil field equipment

Petroleum prospecting

Economic and social effects

Sedimentology

Petroleum reservoirs

Coal

Coal deposits

Coal industry

Gases

Productivity

Dynamics

Bearings (machine parts)

Oil bearing formations

Drainage

Hydrocarbon seepage

Natural gas wells

Tight gas

Water supply systems

Coalbed methane, shale gas and tight gas within coal measures exist simultaneously in many basins worldwide, with the successful exploration and development of specific gas respectively. However, the multi-layer/multi-unconventional natural gas development in the same wellbore has not yet been systematically implemented. The realization of multi gas collaborative development will greatly improve the availability of underground resources and economic benefits. This paper systematically summarizes the development and understanding of hydrocarbon generation evolution, gas reservoir occurrence, reservoir physical properties and production mechanism of coal bearing gas occurrence in typical basins in order to provide theoretical and methodological reference for unconventional gas multi gas co-production. The main progresses include the overpressure or micro-fissure during hydrocarbon generation of coal measures is the necessary condition for gas diffusion and migration continuously to adjacent layers

coal bearing gas system presents the characteristics of box sealing, continuous migration and accumulation, dynamic transformation and directional accumulation and dispersion

static geological parameters such as strata combination, stress field, temperature field and gas bearing property determine the recoverability, and dynamic parameters such as single/multi-layer phase permeability, reservoir pressure and liquid supply capacity determine the production performance

physical experiment and numerical analysis can simulate the interference factors of combined mining under ideal geological conditions, and reservoir pressure and permeability are the main factors affecting the seepage in drainage period and gas water production period

and a reasonable drainage gas production process and scientific control of gas production speed can properly avoid or control the interference between layers and in the wellbore. The key in co-production research is "geology+engineering" dessert area selection. The key problems needed to be solved include the dynamic migration and accumulation process of superimposed multi type gas reservoirs in the geological evolution process, and the formation and recognition criteria of dominant reservoirs

the complex gas-water distribution relationship and fluid pressure system in coal measures, and how to ensure the effectiveness and scientific monitoring of stimulation measures

and the multi-layer combined production and drainage control system and productivity prediction method. The detailed works are to clarify the dynamic processes of coal measures sedimentary, reservoir diagenesis, hydrocarbon generation and migration, and gas-water occurrence and flow state. The technical sequences are geological selection, drilling and completion and reservoir protection, stimulation and transformation technology, drainage system and productivity prediction. According to the coexistence characteristics of multi-layered unconventional natural gas in coal measures in different areas, choosing appropriate technology to realize co-production within one wellbore will significantly reduce development costs, improve economic benefits and resource utilization. 2020, Editorial Office of Journal of China Coal Society. All right reserved.

1406-1418

45

Meitan Xuebao/Journal of the China Coal Society

2020

Li, Yong

Wang, Yanbin

Meng, Shangzhi

Wu, Xiang

Tao, Chuanqi

Xu, Weikai

journalArticle

2539993

10.13225/j.cnki.jccs.2019.1305