Feasibility Analysis and Optimal Design of Acidizing of Coalbed Methane Wells

Abstract

Plugging is a prominent reason for production reduction in coalbed methane (CBM) wells. In order to solve this problem, authors conducted the feasibility analysis and optimal design of acidizing of CBM wells to remove the plugging in Hancheng block (H block) China. First, X-ray diffraction analysis shows that the plugging contains acid-soluble minerals and the field case indicates that acidizing effect is positively correlated with the content of acid-soluble minerals. Inspired by this, authors analyze determining factors of the content of acid-soluble minerals. Well logging parameters (DEN, AC, GR) are selected to establish a neural network model to predict the content of acid-soluble minerals. Furthermore, a feasibility criterion of acidizing of CBM wells is proposed. Then, a forward model and an inversion algorithm are proposed to diagnose the plugging. The multisolution problem of parameters inversion is solved by the Gauss–Marquardt (G-M) algorithm based on the stochastic initial value and maximum probability. Combining this method with the current numerical model of acidizing, authors present an optimal design in order to optimize the volume and injection rate of the acid. Meanwhile, by experimental study, authors propose a new acid formulation. Finally, results have been applied in the field to confirm the feasibility of the acidizing. It turns out that acidizing is an effective stimulation technology for some specific CBM wells, and the feasibility analysis and the optimal design can improve the effect of acidizing of CBM wells.

3D Fracture Propagation Simulation and Pressure Decline Analysis Research for I-Shaped Fracture of Coalbed

“…The mutual influence of many factors leads to this phenomenon, such as the existence of the coalbed cleats at the interface of coalbed and cover/bottom layer [9], the large differences in the mechanical properties between coalbed and cover/bottom layer, tectonic stress of coal seams, coal blockage, interface effects of different lithologies [10,11], etc. The T-shaped and I-shaped fracture have been found in some realistic areas, and they were directly observed after HF [12]. Meanwhile, Guo et al [13] and Tang et al [14] have proved the existence of these kinds of fractures.…”

Theoretical and experimental determination of proppant‐crushing ratio and fracture conductivity with different particle sizes

“…3,4 A significant amount of proppant is used in hydraulic fracturing. [5][6][7] The currently low price of oil has a serious negative impact on the production of various oil fields. 8 For example, in the exploitation of tight oil reservoirs, existing fracturing technology can produce economic benefits at high oil prices, but at low oil prices, the development cost of tight oil and gas reservoirs is greater than the benefit of the output.…”

“…8 For example, in the exploitation of tight oil reservoirs, existing fracturing technology can produce economic benefits at high oil prices, but at low oil prices, the development cost of tight oil and gas reservoirs is greater than the benefit of the output. 7 Therefore, one of the most urgent tasks in developing oil and gas fields is to "reduce cost and increase efficiency". 8 Proppant-crushing ratio and proppant fracture conductivity are two main indicators of proppant performance, 9,10 as well as being important parameters in proppant selection, 11,12 fracture design, 13,14 and postfracture evaluation.…”