Maximizing Hydrocarbon Potential in Marginal Field Using Data Integration Techniques, A Case Study from the Saraswati Field, Barmer Basin, India

Abstract

Abstract Saraswati Field, located in south-central part of hydrocarbon prolific Barmer Basin is a marginal field and has been developed with a cautious approach to address high degree of uncertainty. The paper summarizes the robust workflow considered for a complete phased re-development approach by leveraging state-of-the-art multi-disciplinary data integration techniques aiming to access the true potential through maximizing the productivity while mitigating uncertainties associated with reservoir characterization for minimizing risk. The stratigraphy of the Saraswati field can be divided into five different zones based on sedimentological analysis, Barmer Hill, Fatehgarh Zone-1, Fatehgarh Zone-2, Ghaggar Hakra Zone-1, and Ghaggar Hakra Zone-2. The primary focus of this paper is Fatehgarh Zone-1 reservoir, which is a mix of sandstones and shale deposited following a major hiatus / non-deposition of Late Cretaceous age. The upliftment and erosion lead to thinning of Fatehgarh towards northern part of the field. A conceptual geological model was prepared in the light of data integration technique including reprocessed seismic data, resulting in improved structural and stratigraphic control. Detailed core studies have provided a better understanding of lithofacies, leading to a substantial increase in net-to-gross. Additionally, production data revealed that the well is drawing oil from a larger volume, further supporting the geological model's assumptions. A customized seismic reprocessing flow helped in enhancing the frequency content with better temporal resolution and higher signal to noise ratio. Furthermore, the seismic attribute study of the Fatehgarh interval had established that the sand prone zones are characterized by low RMS amplitude, which was also confirmed by low instantaneous frequency and low amplitude in the Spectral Decomposition study. Core data analysis in Fatehgarh formation suggested presence of considerably more reservoir facies in the system compared to what is visible in wireline log. Drill cuttings data from wells across the field also indicated presence of higher proportion of sand and silt. Image Log data supports this fact indicating presence of thin bed pay which are beyond log scale resolution. Based on the production performance of Saraswati field, material balance model was worked upon considering production data and shut-in pressure for Saraswati wells for back calculating the in-place volume. The stabilized shut-in pressure in producer wells draining from Fatehgarh reservoir have indicated a three times upside in STOIIP for Fatehgarh reservoir. An updated static model was prepared capturing all the above- mentioned studies which results in nearly three times upside in the STOIIP estimation and opens opportunity for further development plan with more confidence on reservoir distribution. The project has successfully integrated multi-disciplinary information from Geology, Geophysics, Petrophysics and Reservoir Engineering, by creating a comprehensive framework for the associated uncertainties of the marginal field with limited well penetrations. Through this synchronization, the project has achieved critical inputs towards a full field development with implementation of newer concepts like planning near horizontal well with hydrofracking for thin bed reservoir to unlock the full potential.