Gas Storage Performance in a Fractured Formation

Gas Storage Performance in a Fractured Formation Lubomir G. Gerov; Lubomir G. Gerov U. of Mining and Geology Search for other works by this author on: This Site Google Scholar Shteryo K. Lyomov Shteryo K. Lyomov U. of Mining and Geology Search for other works by this author on: This Site Google Scholar Paper presented at the SPE Gas Technology Symposium, Calgary, Alberta, Canada, April 2002. Paper Number: SPE-75678-MS https://doi.org/10.2118/75678-MS Published: April 30 2002 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Gerov, Lubomir G., and Shteryo K. Lyomov. "Gas Storage Performance in a Fractured Formation." Paper presented at the SPE Gas Technology Symposium, Calgary, Alberta, Canada, April 2002. doi: https://doi.org/10.2118/75678-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE Unconventional Resources Conference / Gas Technology Symposium Search Advanced Search AbstractThis paper presents analysis of the performance of Chiren Underground Gas Storage Field located in Northwest Bulgaria. The storage was built in a depleted gas condensate reservoir. The producing formation comprises of fractured multi layered carbonate and sandstone rocks. The gas field/storage has been object of several controversial studies.The paper includes analysis of the influence of rock deformations, water drive, and effect of the capillary processes, from the period of gas field to the recent days. In the study, data from the 30 years history period, laboratory data as well as mathematical simulation are used.The results show significant influence of the heterogeneity of the formation, production injection schedule, and the well spacing. Progressive time dependent gas dis-balance is observed. Evaluation shows that it is in the range of 1/3 the peresent stored gas volume in the reservoir. Well logs prevail good state of the production casing and luck of gas migration in upper formations. Simulation shows that the main reasons for the gas dis-balance and formation of zones with higher pressure as a result of water movements, formation rock deformation and well water cut. The inadequate reservoir management has neglected those factors and it seems it's the main reason for the bad reservoir performance.IntroductionGas storage operation depend on the state and performance of the reservoir. Decisions to increase cushion, working gas volumes and deliverability of the storage, drilling new wells as well as abandoning existing must be based on analysis and simulations to define the working envelope and investments. Otherwise the risk to provoke gas losses due to migration, blocking and fingering is high12,13.Fractured reservoirs with pronounced rock deformations and with aquifer systems are difficult to predict and simulate. Understanding the history of the gas field and gas storage development is essential in the managing successful operations. The only one Bulgarian gas storage field Chiren lately shows signs of unstable reservoir performance with considerable dis-balance in its inventory. This fact can be crucial in the decisions for storage expansion and its future operations.In the paper analysis of the data for whole period of the field/storage development is presented. The term gas dis-balance is defined and simulation model presented.Chiren gas condensate field geologyChiren gas condensate field is located in Northwest Bulgaria. Field production started 1965 and the reservoir was depleted in 1974. Chiren gas condensate field is brachial anticline structure Figure 1. With respect to isohypsis -1750 m structure sizes are 14×5,5 km. The reservoir is massive type with maximal total thickness about 400 m, and initial GWC at −1675 m. The initial formation pressure was 18,1 MPa and formation temperature 75 degC. The producing formation is presented by limestone, dolomites and sandstone divided 4 layers. They are Lower Triassic (T1) Middle - Upper Triassic (T2+3), Hetangian - Sinemurian (J11) and Pleinsbachian (J12). Layers T2+3, J11 and J12 are fractured, while T1 is whitout developed fracture system. Porosity of the rocks varies within 1 to 2,8% (T2+3), 1 to 5,5 (J11), and 0,92 to 2,0 for (J12). The lab measured fracture porosity is 0,1%. Permeability of the block matrix measured is lower that 1E-15 m2, while the one calculated from well testing is 3 to 150E-15 m2. Keywords: accumulative gas production, gas storage, reservoir management, upstream oil & gas, reservoir performance, field development, gas dis-balance, complex reservoir, natural gas storage, sofia Subjects: Formation Evaluation & Management, Unconventional and Complex Reservoirs, Storage Reservoir Engineering, Natural gas storage This content is only available via PDF. 2002. Society of Petroleum Engineers You can access this article if you purchase or spend a download.

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