Integrated Approach to Unconventional Reservoir Characterization: Key for Understanding Hydrocarbon Production Challenges in Kerogen and Tight Fractured Deep Carbonate Complex in Kuwait
- Mihir Narayan Acharya (Kuwait Oil Company) | Mir Md Rezaul Kabir (KOC) | Saad Abdulrahman Hassan Al-Ajmi (Kuwait Oil Company) | Noura Mai'a (Kuwait Oil Company) | Ashok Kumar | San Prasad Pradhan (Kuwait Oil Company) | Ealian H.D. Al-anzi (Kuwait Oil Company)
- Document ID
- Society of Petroleum Engineers
- SPE Asia Pacific Oil and Gas Conference and Exhibition, 22-24 October, Perth, Australia
- Publication Date
- Document Type
- Conference Paper
- 2012. Society of Petroleum Engineers
- 4.3.4 Scale, 4.2.3 Materials and Corrosion, 5.2.1 Phase Behavior and PVT Measurements, 1.14.1 Casing Design, 4.1.5 Processing Equipment, 2.2.2 Perforating, 5.8.1 Tight Gas, 5.8.8 Gas-condensate reservoirs, 5.6.1 Open hole/cased hole log analysis, 4.1.2 Separation and Treating, 1.14 Casing and Cementing, 3.3.1 Production Logging, 5.1.2 Faults and Fracture Characterisation, 5.1 Reservoir Characterisation, 1.10 Drilling Equipment, 5.6.4 Drillstem/Well Testing, 5.6.3 Pressure Transient Testing, 5.1.1 Exploration, Development, Structural Geology, 3 Production and Well Operations, 5.2 Reservoir Fluid Dynamics, 1.6.9 Coring, Fishing, 5.8.7 Carbonate Reservoir
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The unique Kimmeridgian-Oxfordian complex of unconventional and fractured carbonates has been tested to be prolific producer of gas, condensate and light oil in different wells discovered in various North Kuwait fields. The challenge is to characterize the complex reservoir flow system where critical reservoir parameters such as reservoir type, porosity and permeability characteristics, and production and pressure data can vary substantially.
The relationship between the natural fractures and the tight matrix in controlling effective system conductivity in reservoir flow units are the key features which dictate the nature of inflow mechanisms thus the production performance. The paper deals with developing an effective methodology which integrates the variations in critical reservoir properties of the low porosity yet naturally-fractured carbonate reservoir.
The drill stem test (DST) results in some wells were successful without stimulation, while in other wells the DSTs were unsuccessful in spite of advance and repeated stimulations, thus categorizing these plays as geologically-complex, tight gas condensate reservoirs where out of ordinary stimulation techniques may be needed to activate the fractured matrix. Pressure transient analyses and flow regime interpretation of the successfully-tested wells confirm the dual porosity flow-system and the fractured nature of the reservoir.
In this paper, the authors will discuss a new integrated approach for understanding the production and pressure behavior in light of the unique unconventional reservoir characteristics along with the fractured reservoir properties. Dual-layer and dual poro-perm models for pressure transient analysis have been applied extending the previous study of relationship developed between the productivity index (PI) and the total organic carbon (TOC). The proposed integrated methodology can significantly improve the current approach to production optimization, reservoir management strategy, completion, and stimulation design in fractured tight gas condensate reservoirs in Kuwait as well as in other regions.
In the previous study, Acharya et. al., 2009, observed the drill stem test (DST) success trend in the wells tested in the secondary targets in the kerogen and tight-fractured deep carbonate resercoir complex, across multiple fields in the study area in North Kuwait, is being controlled by the unconventional parameter. As the test results in several vertical wells had a positive to negative ratio of 1:1, where, the negative DSTs were either no-flow or no-hydrocarbon, in spite having all other conventional reservoir parameters comparable. This has become quite critical to establish an integrated understanding of the factor of successful unconventional reservoirs tests in multiple vertical exploratory wells, being linked to average total organic carbon (TOC) content of the particular sub-unit in the stacked reservoir sequence (Acharya et. al. 2009). The wells having average TOC content below 2.45% in the NJM unit have positive test results during initial DSTs. Average organic richness in term of total organic carbon (TOC) for NJK and NJM units in the fields under study is very high up to 12.5 wt % and up to 4.5 wt % respectively (Acharya et.al, 2009).
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