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Sharma, Varun (Schlumberger Oilfield Srvcs) | Dasgupta, Sagnik (Schlumberger) | Mahesh, Arathi L. | Sharma, Sachin Kumar (Schlumberger) | Barua, Indrajit (Oil India Ltd.) | Bharali, Binayananda (Oil India Ltd.)
Abstract The Lower Tipam sandstone reservoir of Miocene age in the Jaipur oilfield lies within a highly folded and faulted Assam-Shelf basin, in the north eastern part of India. The analysis of this mature field carries a lot of interest not only because the sands within the formation are hydrocarbon bearing but also because of the complexities associated with its evaluation. The complexities in general relate to a heterogeneous reservoir with complex mineralogy, varying water salinities across the field which makes the visualization of a conceptual geological model in the presence of a complex structure a real challenge. The objective of the study was thus to characterize the reservoir at wellbore level and conduct realistic inter-well and reservoir-scale geo-modeling for improved oil-field development by means of a comprehensive, interdisciplinary approach. The Jaipur area is mainly characterized by a Tertiary terrigenous sedimentary sequence comprising of fluvial to deltaic deposits overlying the Precambrian metamorphic Basement. The reservoir is oil bearing without a gas cap. The clay typing and the salinities of water bearing zone have an important bearing on the hydrocarbon saturation computation. Based on the available core data, production data and the volumetric computation at wellbore level using ELANPlusTM, the field portrayed oil occurrence in a unique pattern when visualizing the 'oil down to' i.e. OWC, oil-shale contact (OSC) and wells with residual oil saturation. The pattern appeared unusual in a homogeneous clastic reservoir. The OWC depth in the reservoir showed variations across the field, suggesting the presence of a fault network which also controlled the hydrocarbon entrapment. These faults were not easily identifiable from seismic interpretation; the discrete fault network of the area was analyzed by a process of automated fault identification. Though the difference in the OWC encountered in the wells could be explained based on the sealing faults barriers picked up in the area, but the pattern of the depths of OWC, OSC and distribution of wells with residual oil saturation areally suggests the presence of a stratigraphic trap within the formation. The 3D seismic volume was analyzed to understand the extent of the sand body forming the stratigraphic trap and to define its morphology. Iterative analyses of the seismic attributes suggested the possible geometry of the sand body. Using the log interpretation, an isochore was prepared as per the evolved morphology of the sand and was used for modeling the sub zones. The rock types were modeled geo-statistically to define the spatial heterogeneity and to visualize the distinct compartments within the reservoir. Using single well predictive modeling, the flow units and the petrophysical rock types were defined and the water saturation in the 3 dimensional spaces was modeled through saturation height function for each of the reservoir rock types which were later used for HCIIP calculations. As a result of this study the geo-cellular model of the Lower Tipam reservoir was prepared incorporating a better understanding of the spatial heterogeneity, flow unit definitions and the fault compartmentalizatio
ABSTRACT: The precipitation is the main source of the recharge of the ground water and mainly controlled by geology, geomorphology and Landuse-landcover (LULC) pattern of watershed area. In some situation particularly in area having less precipitation and no perennial recharge system water may be imported to artificially recharge the permeable zones for augmenting the groundwater availability. In order to have an efficient and effective recharge system it is imperative to have well defined permeable zones. Therefore the identification, characterization and delineation of the permeable zones of a selected watershed area becomes important for development and planning of ground water. The present study,, deals with a systematic study consisting of visual as well as digital interpretation of IRS multispectral data which lead to delineate different permeable zones in a milliwatershed in Jaipur district of Rajasthan India. The characteristic features of each unit of thematic maps have been integrated to delineate the Recharge, Discharge and Intermediate zones. Discharge zones have been mainly found along the major drainage line, in depressions, and plain area. Agricultural land has been identified as recharge area while intermediate zones found in between these two areas. Fallow land has been identified as both recharge and intermediate zones.. The finding may be replicated in other similar areas to delineate the zones with fair accuracy and precession. INTRODUCTION Ground water is an important source of water for domestic, industrial and agricultural purposes. Unfortunately, ground water is being used extensively and therefore water levels are falling down indiscriminately. Dense and rapidly increasing population requires both large amount of water for drinking, agricultural and industrial purposes (Sinha, Dubey and Yadav, 1999). Wide spread haphazard pumping may produce a number of undesirable consequences such as reduction in the available water supply, deterioration in water quality and increased pumping costs.