Patterns and pilot project demonstration of coal measures gas production

Occurrence state and reservoir properties of coal measures gas (CMG) are complex and variable,so that the pattern of economic and efficient CMG production is still in the initial stage. For this reason,the progress of the research and field test for the production patterns in recent years in China is analyzed,the current understanding of the patterns is summarized,and the applicability and limitations of different patterns are compared. Then,taking the demonstration project in Linxing block as an example,the types and joint production effectiveness of production curves are discussed,and the successful examples of joint CMG production are introduced. Based on the string structure design and drainage control measures,combined with the selection of well pattern and fracturing method,the CMG production process is preliminarily classified into three patterns,i. e. layering,first layering then joint,and joint drainages. Each pattern includes several specific methods,each of which has its own advantages and disadvantages. The main methods in layering and joint drainages have preliminary effect in application,and those of the first layering then joint drainage are still in design and even idea. It is suggested that the CMG production pattern and its innovation should be based on some strategies,including adjusting measures to local conditions,learning from each other’ s strengths to make up for each other’ s weaknesses,combining multiple channels and focusing on some aspects,and the adaptive production technology should be selected and developed according to the specific geological conditions of the gas reservoirs. At present,only two national demonstration projects have promoted the innovation of CMG production pattern in China.The scale CMG development in the Linfen demonstration area has been rapidly extended by adopting the method of partition and separate production,and the economic and efficient joint production of various types of CMG has been realized in the Linxing demonstration area by developing the technology of the induced control continuation through pressure drop with exhausting gas. The analysis of the demonstration effect of the CMG production project is focused to the Linxing demonstration area,which reveals the CMG production law under a natural continuation method. It is found that there are four types of single well production curve,including the type I curve characterized by the multi-layer commingled production of desorption gas,the type Ⅱ and type Ⅲ curves characterized by the commingled production of free and desorption gases induced continuation production,and the type IV curve of the single free gas production.The project demonstration results show that the effective joint CMG production can be realized under a wide range of gas reservoir conditions by using the induced continuation method of the pressure drop with exhausting gas,which is a new way of economic and efficient joint CMG production worthy of further research and application. It is worth noting that all types of CMG reservoirs with an industrial value exist in the deep strata where the water richness is often weak,which limits the traditional pattern “ drainage and pressure drop”. However,the induced control continuation production through pressure drop with exhausting gas can make up for this major limitation,which is of universal significance for the economic and efficient CMG development.