Abstract

Karachaganak field is one of the largest accumulations of gas-condensate in the world. Located in the northern Pre-Caspian Basin (Kazakhstan), the field is a Permo-Carboniferous isolated carbonate platform with a hydrocarbon column of about 1500 m. In production since 1985, the actual development focuses the oil rim with gas injection implemented, since 2004, in a confined area of the Platform Interior.

Various future development scenarios are now being considered to more fully develop the reservoir, and some of the recovery processes being modeled require an improved understanding of the internal reservoir architecture. In fact the internal reservoir architecture is rather complex, affected by the initial development of aggrading mounds followed by progradation (consisting most likely in a clinoform geometry) passing to cyclic, grain-dominated platform interior sediments. The resulting reservoir quality is quite heterogeneous with low porosity but locally high productivity when affected by micro-fractures and vugs. In this context a deep analysis has been performed considering the location of additional injection in different areas/regions of the field evaluating the possible risks and the uncertainties affecting the liquid recoveries. Nine different areas characterised by specific geological/dynamic behaviour have been investigated. Moreover considering the Prograding area, alternative models were built in order to address the possible impact of Clinoforms on the flow patterns. The final analysis, which takes into consideration the possible liquid recovery and the relevant knowledge and complexity of the different areas, provided an improved view to optimize the future injection. In fact, the Cyclic Platform, where injection has been already implemented, appears to be the best candidate; other areas, although affected by a certain degree of uncertainty, also seem promising from the recovery point of view, while some other regions, characterised by high compartmentalisation, appear to be less interesting.

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