A new method for well pattern density optimization and recovery efficiency evaluation of tight sandstone gas reservoirs

Research on the Definition of Economic Limits for the Development of Unconventional Natural Gas under New Situations

“…For well density design, the general approach [2] is to design several possible well spacings for the development, estimate the gas output with such methods as numerical simulation, calculate economic benefits according to the estimated output, and select the best well density according to the comparative benefits. e research mainly focuses on the impact mechanism of well density on the final output, for instance, the impact of different well densities on the recovery ratio [3]; although some researchers, considering the time value of funds [4], have chosen the discounted cashflow method to calculate the economic limits of well density, they failed to consider such realistic situations as changes in the prices and subsidies in the future. e design of drilling depth is less subjective than that of well density because the depth of the gas-bearing layer is often determined objectively, and the research on depth limits is generally in engineering and technical perspectives, such as drilling methods [5], reservoir forming conditions [6], changes in reservoir conditions [7], and brittle ductility [8].…”

“…As for shale gas, China's shale gas is mainly produced in Chongqing and Sichuan. In 2018, Fuling in Chongqing produced 6.02 billion m 3 of shale gas, and the shale gas output of PetroChina in Sichuan was 4.27 billion m 3 . erefore, the producer price indexes of oil and natural gas exploration industries (O&G PPI) in Chongqing City and Sichuan Province were selected as the price indexes of shale gas weighted according to this proportion.…”

“…(3) e growth rate of the output of unconventional natural gas is slowing down: although China's unconventional natural gas is still developing rapidly, the growth rate is decreasing. Since 2016, the annual output of the CBM industry has been kept at 7 billion m 3 , with no new growth [1]. e annual output of tight gas increased by 126.7% (from 15 to 34 billion m 3 /year) from 2009 to 2013, while in the last 5 years (2014 to 2018), it increased only by 27% (from 37 to 47 billion m 3 /year); shale gas exploitation started late, with the commercial gas flow formed in 2013. e annual output increased by about 3 billion m 3 before 2015 while only by about 1.5 billion m 3 after 2015 (Source: Historical news reports, annual reports and statistical yearbooks of the National Bureau of Statistics and the National Development and Reform Commission).…”

Single well control area splitting method based on reservoir sphysical properties and gas well productivity differences

“…With the development of gas reservoirs, in order to further clarify the remaining geological reserves and the distribution of remaining oil and gas on the plane well points, it is necessary to calculate the geological reserves of a single well, and the calculation of the control area of a single well is the top priority of determining the geological reserves of a single well. In general, the current methods for calculating the control area of a single well are mainly divided into three types: empirical formula method [1][2][3] , area trade-off method [4][5][6][7] , and physical model [8][9][10] . Among them, the empirical formula method uses pressure recovery well testing as a means to obtain calculation data, but for low-permeability gas wells, the pressure recovery time is long and it is difficult to obtain accurate data; the area trade-off method is based on the triangulation algorithm, but it believes that single well control The range is within 1/2 of the distance between adjacent wells, and the influence of the heterogeneity of the actual gas reservoir on the control area of a single well is not considered, which is contrary to the actual situation; the physical model method uses the logging interpretation data to perform geological modeling.…”

Investigation of Gas-liquid Separation Experiment of Electric Pump Drainage and Gas Extraction Unit in High Gas-liquid Ratio Gas Wells

“…Meanwhile, water in the formation sealed off the reservoir, which made it impossible to recover a large amount of natural gas reserves effectively and drastically reduced the recovery rate [2] . Drainage gas extraction was a technological measure to solve the problem of excessive fluid accumulation or water production in the formation near the wellbore and well bottoming and to restore the gas well to normal production, the purpose of which was to delay and avoid flooding of the gas wells, improved the production condition of the gas reservoir, and increased the efficiency of gas reservoir development and recovery rate, which had a pivotal role in the development process of the gas field [3] . At present, the principle of gas drainage is mainly from the gas dynamics method [4] , physicochemical method [5] , and artificial lifting method [6] .…”