Drilling and completion technologies of coalbed methane exploitation: an overview

Abstract

Coalbed methane (CBM) drilling and completion technologies (DCTs) are significant basis for achieving efficient CBM exploration and exploitation. Characteristics of CBM reservoirs vary in different regions around the world, thereby, it is crucial to develop, select and apply the optimum DCTs for each different CBM reservoir. This paper firstly reviews the development history of CBM DCTs throughout worldwide and clarifies its overall development tendency. Secondly, different well types and its characteristics of CBM exploitation are summarized, and main application scopes of these well types are also discussed. Then, the key technologies of CBM drilling (directional drilling tools, measurement while drilling, geo-steering drilling, magnetic guidance drilling, underbalanced drilling and drilling fluids), and the key technologies of CBM completion (open-hole, cavity and under-ream completion, cased-hole completion, screen pipe completion and horizontal well completion) are summarized and analyzed, it is found that safe, economic and efficient development of CBM is inseparable from the support of advanced technologies. Finally, based on the current status of CBM development, the achievements, existing challenges and future prospects are summarized and discussed from the perspective of CBM DCTs.

Analytical Model of Wellbore Stability Analysis of Inclined Well Based on the Advantageous Synergy among the Five Strength Criteria

“…The EMW of collapse pressure was between 0.75 g/cm 3 and 0.89 g/cm 3 , and the horizontal well deviated ~45 °from the σ H direction had the best stability, while the vertical well had the worst stability, and the stability of horizontal and highly deviated wells parallel to the σ H direction was slightly better than the σ h direction (6) As shown in Figure 5(f), for this new CPM, the EMW of collapse pressure decreased with borehole inclination along either the σ H direction or the σ h direction. The EMW of collapse pressure was between 0.87 g/cm 3 and 1.01 g/cm 3 , and the horizontal well deviated ~45 °from the σ H direction had the best stability, while the vertical well had the worst stability, and the stability of horizontal and highly deviated wells parallel to the σ H direction was surely better than that of σ h direction (7) For the same well path condition, as shown in Figure 5, the M-C criterion always gave the greatest collapse pressure owing to it ignoring the influence of the σ 2 , followed by this new CPM, the Mg-C criterion, the D-P criterion, the ML criterion, and the MW-C criterion, because the other conventional models involved the different influence of the σ 2 [55,56], and this new CPM integrated the advantageous synergy of the five different criteria 4.3. WSA Results under RF Condition.…”

“…The EMW of collapse pressure was between 0.67 g/cm 3 and 0.94 g/cm 3 , and the inclined well (ψ ≈ 60 °) along the σ H direction had the best stability, while the horizontal well along the σ h direction had the worst stability, and the stability of horizontal and highly deviated wells parallel to the σ H direction was surely better than that of σ h direction (6) As shown in Figure 6(f), for this new CPM, the EMW of collapse pressure slightly increased with borehole inclination along the σ h direction, while it firstly decreased and then increased slightly with borehole inclination along the σ H direction. The EMW of collapse pressure was between 0.80 g/cm 3 and 1.05 g/cm 3 , and the inclined well (ψ ≈ 60 °) along the σ H direction had the best stability, while the horizontal well along the σ h direction had the worst stability, and the stability of horizontal and highly deviated wells parallel to the σ H direction was surely better than that of σ h direction (7) For the same well path condition, as shown in Figure 6, the M-C criterion always gave the greatest collapse pressure owing to it ignoring the influence of the σ 2 , followed by this new CPM, the Mg-C criterion, the ML criterion, the D-P criterion, and the MW-C criterion, because the other conventional models involved the different influence of the σ 2 [55,56], and this new CPM integrated the advantageous synergy of the five different criteria 4 and Table 3, for the same well path under the NF condition, the M-C criterion always gave the greatest collapse pressure (1.16-1.45 g/cm 3 ), followed by this new CPM (0.96-1.22 g/cm 3 ), the Mg-C criterion (0.93-1.17 g/cm 3 ), the MW-C criterion (0.84-1.12 g/cm 3 ), the ML criterion (0.88-1.11 g/cm 3 ), and the D-P criterion (0.82-1.17 g/cm 3 ). As shown in Figure 5 and Table 3, for the same well path under the SSF condition, the M-C criterion always gave the greatest collapse pressure (1.07-1.22 g/cm 3 ), followed by this new CPM (0.87-1.01 g/cm 3 ), the Mg-C criterion (0.85-0.97 g/cm 3 ), the D-P criterion (0.79-0.96 g/cm 3 ), the ML criterion (0.81-0.93 g/cm 3 ), and the MW-C criterion (0.75-0.89 g/cm 3 ).…”

“…Owing to advances in directional drilling technologies, directional, horizontal, and extended-reach wells are widely employed to develop these unconventional petro-leum reservoirs [5,6]. Although these types of nonvertical wells, particularly, horizontal wells, are much more expensive than that of vertical wells, they are more popular owing to their advantages in enhancing oil and gas production, lowering surface well pad construction, and lowering comprehensive development cost [7], so they have become very valuable techniques in recent years. However, in the process of drilling such types of inclined wells, the engineers usually encounter some complicated problems, such as high risk of wellbore instability [8], excessive drill-string drag [9], hole cleaning in highly deviated wellbore [10], and high risk of pipe sticking and casing wear [11], which will cause long nonproductive time, long drilling cycle, and high drilling costs [12,13].…”

Prediction Method of Coal Texture Considering Longitudinal Resolution of Logging Curves and Its Application─Taking No. 15 Coal Seam in the Shouyang Block as an Example

“…Coal texture, as an observable manifestation of the degree of structural deformation, significantly influences the physical characteristics of the coal reservoirs, the selection of fracturing layers, and the development outcomes. Consequently, it serves as a crucial indicator for evaluating coalbed methane reservoirs. , The No. 3 coal seam of Shanxi Formation and the No.…”

The Infrared Radiation Characteristics of Sandstone Fracture Seepage under Coupled Stress-Hydro Effect

“…With the rapid development of social construction, many cities worldwide have taken the development and utilization of underground space as an important way to solve the population, resource and environmental crises and implement the concept of sustainable development [1][2][3][4][5][6][7][8][9]. However, the development of underground space and other geotechnical engineering is often restricted by groundwater [10][11][12][13][14][15][16][17].…”