Gas-water phase flow production stratified logging technology of coalbed methane wells

On the basis of the previous development of cumulative gas flow meter, a set of integrated coalbed methane (CBM) well production test instrument is developed and applied in field to solve the problem of gas-water phase flow production stratified logging test. This instrument uses a cumulative gas flow meter to test stratified gas production, which can be flexibly converted into a capacitive water holdup meter underground to obtain water holdup. Fluid flow rate can be measured by the converted capacitive water holdup meter combined with a gamma tracer flow meter, and hence stratified water production can be calculated. The instrument meets the gas and water production synchronous measurement and integrated miniaturization. A dynamic seal pressure balancing technology is applied to solve the unbalance between internal and external forces of pressure cylinder when down-hole piston is open in the well. The use of novel releasable guide cone to replace the squirrel cage guide cone effectively solved the difficult problem of the instrument entering the CBM well. With a diameter of only 22 mm, the instrument can be run in to the annulus through an eccentric wellhead. In field test the gas and water production of different layers can be obtained using declining method by placing the instrument at different coal seams, to evaluate gas and water production of different layers in commingle production CBM wells. Field application shows that the instrument has the advantages of small size, high measuring precision, short measuring time, and no disruption on well production, etc., and exhibits a broad application prospect in CBM development.