Development and application of a coal reservoir protection device

Coal reservoirs can be damaged easily due to the large specific surface area, high stress sensitivity and strong absorbability.Eventually, the coalbed methane (CBM) recovery factor is adversely affected. A coal reservoir protection device for CBM wells was developed to reduce the damage on coal reservoirs during the workover. According to its design, the valve assembly which is used to control the unidirectional flow of fluids in well, works together with the springs in central tube to shut in the flow path in hole with the increasing of pressure difference. In this way, the reservoir is isolated, while the CBM well can perform continuous stable production.The device was tested in 3 wells. As a result, it only took 15% of the original time for the gas production to recover to the previous level.This indicates that the device can isolate and protect the reservoir effectively. Furthermore, it provides a new method and idea for coal reservoir protection during the workover of CBM wells.