Division of Main Geological and Engineering Controlling Types of Low-Production Coalbed Methane Well-Blocks and their Stimulation Measures.

ABSTRACT

At present, the identification of the main factors controlling low-production coalbed methane (CBM) wells and production enhancement measures does not consider geological and reservoir differences between individual wells and the CBM production effect of well groups simultaneously. In view of this, an evaluation index system suitable for use on inefficient well-blocks was established, which involves their geological resource potential, ground stress, coal structure, and comprehensive permeability under engineering influences from a systemic perspective. The main geological engineering types were determined by zoning superposition, and the corresponding stimulation measures were proposed. The evaluation results of the Shizhuang South Block in the Qinshui Basin show that the area of interest can be divided into Class I, II, and III potential areas, of which the Class II potential areas are subdivided into six blocks. In Zone I, the horizontal well infill method is preferred to increase the CBM production from well groups. At the current level of technology, it is difficult to gain economic benefits from Zone III. In Zone II, these stimulation measures such as the infilling method of staged fracturing horizontal wells, refracturing under supplementary injection holes, roof fracturing, the combined method of acidification and secondary fracturing or nitrogen injection and secondary fracturing, the combined method of acidification and controlled displacement secondary fracturing, and controlled displacement repetitive roof fracturing, among others, can be adopted.