A Miscible Hydrocarbon Gas injection pilot is being implemented by Kuwait Oil Company in the Minagish Middle Oolite (MN-MO) carbonate reservoir of West Kuwait. The water pre-flush phase of this pilot was initiated in March 2016 in preparation for subsequent miscible gas injection. An Inter-Well Tracer Test (IWTT) was performed during the water pre-flush phase to assess reservoir conformance and connectivity in a complex and highly laminated formation to support reservoir modeling activities.
Implementing an IWTT is an integral part of the overall surveillance/monitoring program to properly evaluate reservoir heterogeneities within and around the selected pilot area prior to miscible gas injection. Three different tracers were injected through the central injector into three geologically distinct, vertically stacked and inter-connected layers. Water samples were collected from three pilot producers on a regular basis for lab analysis to construct produced tracer curves. These tracer curves were then characterized analytically and compared with the original pilot performance forecasts that were generated using a reservoir sector model.
Tracer data showed reasonable breakthrough times and distinct peaks representing different flow paths for every injector-producer pair, involving one injector and three surrounding producers. Analytical interpretation of tracer data was useful to assess ultimate tracer production and swept volumes for each flow path. Based on the observed tracer breakthrough times during the water pre-flush phase, it can be inferred that limited preferential flow is expected during the subsequent miscible gas injection phase. The data from the above-mentioned IWTT and ensuing analytical characterization can be integrated with the on-going simulation activities to generate more reliable performance forecasts for miscible gas injection into the MN-MO carbonate reservoir.
This paper highlights how analytical interpretations can be derived for multiple flow paths in relation to water and miscible gas injection using IWTT data. The results from this study are important to enhance and fine-tune the reservoir simulation models that are being used in the meantime to generate reliable performance forecasts.