Fractures play a major role in the production from low permeability carbonate reservoirs. In this paper, an integrated approach for fracture characterization using seismic attributes is attempted. In order to get better detection and interpretation of fractured zones, multi seismic attributes including volume curvature, coherency etc. were applied to reduce the uncertainties associated with the seismic data, and some geological constraints including faults-associated fracture zones etc. were used to interpret and identify the fracture features correctly.The Makhul Formation in Kuwait is a tight and low porosity fractured reservoir and is an important target for hydrocarbon exploration. From a preliminary 3D seismic attribute analysis of the area of interest, the attributes of curvature (positive and negative), semblance and ant tracking have been the most helpful tools in predicting where a high density of fractures might exist and their general orientation.

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The challenge of Heavy oil thermal production Kuwait includes how to monitor steam flood effectiveness and cap rock integrity. Due to shallow & heterogeneous reservoirs and thin cap rock, pressurized and heated steam could diffuse in all directions and breach the cap rock. KOC acquired a baseline & time-lapsed surface seismic and 3D VSP for purposes of monitoring CSS production. This paper presents a technical application of seismic inversion to steam chamber size & cap rock integrity interpretation. The seismic image area includes 13 CSS wells, at varying CSS stages of steam injection, soaking and production. The data acquisition consisted of a base and a time-lapsed monitor seismic; each acquisition period lasting for around a week and separated by 40 day intervals. The simultaneous acquisition of surface seismic and the 3D VSP enabled complimentary data exchange and results validation. Well data of sonic and PHIT are used for building a low frequency inversion model. Rock physical modeling is also required to understand the effect of steam and production changes on acoustic and elastic properties. Various geophysical inversion methods are performed on AI inversion of post & pre stack seismic and Poisson's ratio inversion. To estimate reservoir temperature changes due to steam injection, the calibrated rock-physics model was utilized to relate the AI response to temperature change. The steam injection is expected to decrease acoustic impedance. The AI difference exhibits much wider impedance anomalies revealing steam chamber size and the production zone around the wells at various stages of the CSS cycle. Average temperature maps in reservoirs derived from rock-physical modeling also show temperature change around the wells. Inverted seismic attributes of acoustic impedance and temperature were used for study of cap rock integrity. Interpretation results of the steam size through AI and temperature analysis at reservoir and cap rock enable optimization of our CSS and SF completion strategies include steam pressure and volume, soaking period and thermal production control. The result of cap rock integrity monitoring also indicate no serious damage of cap rock under existing conditions of CSS operation (WHT: 420 °F & WHP: 320 PSI), which defines the limits of strategies to increase steam pressure and volume to increase EOR efficiency.

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