The Technology Design For Single U-Type Horizontal Well Exploiting Coalbed Methane Adjacent Formation In Liulin

With unideal coalbed methane production in Liulin demonstration area as the startingpoint, this thesis is to study the gas drilling and completion and drainage methods to improvecoalbed methane production capacity both home and abroad. In view of low porosity, lowpermeability, and low pressure as the features of coalbed methane reservoir, desorption andseepage area is to be expanded in order to improve production, and the currently used drillingand completion techniques are those with vertical/directional well fracturing, U-shaped wells,horizontal wells staged fracturing, multilateral wells, caves, etc. However, it still cannot meetthe need to increase production capacity. The thesis hence puts forward an assumption that asingle U-shaped horizontal well should be drilled, staged fracturing should be adopted on theupper and lower seams, so that multiple coal seams can be drained in the meantime, which iscalled single well commingled technology. Indoor research work and field test work arecarried out to illustrate the actual operational possibility.The thesis proceeds with the physical and chemical properties of the coalbed in Liulindemonstration area and surveys the status quo of gas drilling and completion, fracturing anddrainage when implementing coalbed methane exploration in this area, indicating thenecessity to adopt a single well commingled technology and pointing out the technicaldifficulties currently existing in well type. Considering the characteristics of single U-shapedhorizontal wells, the thesis proposes the following difficulties: maintaining the stability of215.9mm big hole horizontal wells, the completion of horizontal well casing, verticalmultistage fracture of horizontal wells, and the parameter selection of multi-coalbedcommingled drainage.In response to these difficulties, the thesis further applies mechanics experiments, wirelogging information and the simulation software, and carried out prediction researchconcerning the drilling fluid safety density of coal bearing formation, the completion methodsof coal bearing formation, the prediction research of staged fracturing effect of coal bearingformation, the simulation research of horizontal well drainage effect. After comparing theproduction capacity of vertical well fracturing, the thesis determines the feasibility ofexploiting the single U-shaped horizontal wells draining multiple coal reservoirssimultaneously.With over two years of research work, this paper has achieved innovation in two aspects.First, propose and actualize for the first time the multilayer commingled technology of the coalbed methane U-shaped wells. Second, use numerical simulation method for the first timeto simulate the multilayer commingled production capacity of coalbed methane U-shapedwells.