Controls on Gas Storage and Pressure Preservation in a Deep Coalbed Methane Reservoir
Keywords:
Coalbed Methane (CBM), Gas Storage, Formation Pressure, Reservoir Compartmentalization, Petrophysical CharacterizationAbstract
Understanding gas storage and pressure preservation is critical for evaluating deep coalbed methane (CBM) reservoirs. This study investigates the Patchawarra VC50 Deep Coal seam in the Cooper Basin, Australia, through an integrated analysis of gas desorption, methane sorption isotherms, formation pressure testing, and petrophysical characterization. Gas-content measurements indicate raw gas contents of 14.6–20.6 scc/g in coal-dominated intervals, while Langmuir volumes range from 421 to 491 scf/ton (DAF), reflecting strong methane storage capacity. Formation pressure data reveal the coexistence of pressure-preserved and depleted compartments within the Patchawarra Formation, suggesting the importance of reservoir connectivity and pressure compartmentalization. Geochemical analyses show high organic richness (TOC >80 wt%) and thermal maturity within the dry-gas window (mean Ro = 1.46%), whereas mineralogical data indicate contrasting coal- and shale-dominated lithologies. The results suggest that gas retention is influenced by the combined effects of organic richness, adsorption capacity, reservoir isolation, and seal characteristics. The study demonstrates the value of integrating pressure, sorption, geochemical, and mineralogical datasets for deep CBM reservoir evaluation and development planning.
Abstrak
Pemahaman mengenai penyimpanan gas dan preservasi tekanan sangat penting dalam evaluasi reservoir coalbed methane (CBM) dalam. Penelitian ini mengkaji lapisan Patchawarra VC50 Deep Coal di Cekungan Cooper, Australia, melalui analisis terintegrasi desorpsi gas, isoterm sorpsi metana, pengujian tekanan formasi, dan karakterisasi petrofisika. Hasil pengukuran menunjukkan kandungan gas mentah sebesar 14,6–20,6 scc/g pada interval yang didominasi batubara, sedangkan nilai Langmuir volume berkisar antara 421–491 scf/ton (DAF), yang mencerminkan kapasitas penyimpanan metana yang tinggi. Data tekanan formasi menunjukkan keberadaan kompartemen yang mempertahankan tekanan dan kompartemen yang mengalami deplesi dalam Formasi Patchawarra, mengindikasikan pentingnya konektivitas reservoir dan kompartementalisasi tekanan. Analisis geokimia menunjukkan kekayaan organik yang tinggi (TOC >80 wt%) dan tingkat kematangan termal pada jendela gas kering (rata-rata Ro = 1,46%), sementara data mineralogi memperlihatkan perbedaan yang jelas antara litologi batubara dan serpih. Hasil penelitian menunjukkan bahwa retensi gas dipengaruhi oleh kombinasi kekayaan organik, kapasitas adsorpsi, isolasi reservoir, dan karakteristik seal. Studi ini menegaskan pentingnya integrasi data tekanan, sorpsi, geokimia, dan mineralogi dalam evaluasi serta perencanaan pengembangan reservoir CBM dalam.
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