Pre-Feasibility Report Project Details: The Block MB-OSN-2005/1 is a Saurashtra shallow water block situated between GS-OSN- 2003/1(NELP-V) in the west, C-37/C-43 PEL in the east and Saurashtra - Dahanu PEL in the south. The northern side of the block runs approximately parallel to the Saurashtra coast from Diu to Jafarabad township (Fig: 1).The bathymetry within the block ranges from 17 to 37m. Fig. 1: Map showing Location of NELP Block MB-OSN-2005/1 The Block MB-OSN-2005/1 was awarded to ONGC (operator) and GSPC (JV partner) under NELP- VII. The participating interest of ONGC is 80% and GSPC is 20% in the block. The Production Sharing Contract for the block was signed between ONGC, GSPC and GOI on 22.12.2008. The effective date of the contract is 27th January, 2009 with total contract area 2811SKM. The Appraisal area is 1250 SKM and the Relinquishment area is 1561 SKM (Fig: 2) out of the total contract area of 2811 SKM.
Co-ordinates of the Block MB-OSN-2005/1: Latitude Longitude Pt. Deg. Min. Sec. Deg. Min. Sec. A 20 44 56.19 71 30 49.79 B 20 18 12.47 71 02 27.89 C 20 17 59.99 71 14 05.01 D 20 18 00.01 71 29 59.99 E 20 26 44.28 71 29 59.99 F 20 26 44.27 71 31 50.77 G 20 32 36.47 71 31 50.75 A 20 44 56.19 71 30 49.79 Fig. 2: Retained area for Appraisal in block MB-OSN-2005/1
Fig. 3: Seismic Coverage of the entire MB-OSN-2005/1 (NELP-VII) Block
Exploration Periods and Work Program: At present the block is running in Appraisal period (14.10.2013 to 13.10.2016) that is revised and extended from 04.12.2013 to 03.12.2017. Need of the project: The project is a part of exploratory endeavor of ONGC, on behalf of GOI, to find and develop Hydrocarbon. Importance of the project for the country rests in ensuring energy security for the nation. Geological Setup: The acreage is within the continental shelf, situated north of Bombay platform. In North West Diu Arch occupies with a NNW-SSE trending and SSE plunging basement high. It is situated between Saurashtra low in the west and Daman low to the east. The region has undergone Rifting followed by passive continental margin tectonic history with the structural style being dominantly controlled by basement faults, however, the inversion tectonics has also played major role in modifying the existing structural style. The basement architecture of this area has been evolved by the process of rift-drift of the Indian plate. The extensional stresses that were active during the rift phase created number of Horst-Graben features associated with normal faults in the Dharwarian trend i.e., NNW -SSE. There are series of NW-SE trending (Dharwarian trend) deep basinal normal faults present in the study area. The area is characterized by Strike Slip faulting having Transpressional element which have converted paleo lows into present day highs along with Transtensional element & Pure Shear element. So there is a significant structural control which is governing the entrapment mechanism in this area. The generalized stratigraphy is given in Fig: 4. The deposition of Tertiary sediments commenced over the basaltic basement as evidenced in shelf margin wells of Bombay Offshore Block. In Paleocene Early rift and late rift sediments comprising Fanglomerates followed by fluvial and lacustrine deposits are expected to be present and form the base of sedimentation. After marine transgression in late Paleocene-E Eocene the marine sedimentation in post rift phase dominated. This phase has Limestone and shale deposits. In the Early Eocene period carbonate deposition is witnessed over basement controlled morphological highs in some areas and the lows were filled with clastics derived from the adjoining areas. In the Middle and Eocene period extensive carbonate deposition took place, which continued during part of the Early Oligocene in the western part of the block whereas eastern part has dominantly clastic deposition. In the southeastern part, shales and clastics were depositing in the low. Oligocene onwards due to major tectonic activities and westerly tilt of the basin, the depositional regime was dominantly clastic. During Oligocene, shale/clay stones were deposited alternating with occasionally thin limestone. The same depositional environment continued till Mid Miocene period, with the deposition of limestone alternating with shale / clay / claystone. Miocene onwards, the area is characterized by under compacted claystone / shale/silt stone and also sands brought by
submarine channels from the east. This depositional pattern continued through-out the Pliocene period. AGE Seismic Horizon FORMATION LITHOLOGY Recent Pliestocene Pliocene Early Chinchini Dominantly Clay/ Claystone, though coarser clastics are expected towards the northwestern part. Miocene Mid H1A Tapti/ Bandra Dominantly shale with Siltstone bands in to the northeast and Limestone bands developing to the southwest. Early H1C Mahim Shale with few Siltstone. H3CGG Dominantly shale with sandstone beds Daman/ Alibag with few thin coal layers towards the east and limestone beds towards the west. Oligocen e Early H3G Mahuva Dominantly shale with limestone beds. Eocene Mid H3B Diu Shale, siltyshales. Belapur Calcerous shales. Early H4 Paleocen e Early Jafarabad/ Panna Shale and limestone (wackestone) towards Diu arch and sandstone with lignitic coals towards Tapti-Daman area. Cretaceo us H5 Deccan Trap Basalt, weathered basalts. Fig. 4: Generalized stratigraphy of the MB-OSN-2005/1 area
TENTATIVE LOCATIONS OF WELLS IN THE BLOCK Revised DoC for the discoveries in the block is expected to be submitted before 03.12.2017. The upside of the block was evaluated and it was felt necessary to explore the upside locations during DoC - FDP period. The future impetus of exploration in MB-OSN-2005/1 block is towards the North and North-East of MBS051NAA structure. The prospects identified will be upside to MBS051NBA -1 and MBS051NAA-1 development schemes (Fig: 5 & 6). The exact position of the well would be decided on the basis of detailed 3D interpretation of seismic data. Fig. 5: Tentative Prospects shown in Time Structure Map close to Daman Top Estimated Well cost: Cumulative cost for drilling four wells in Prospects A, B, C and D is approximately INR 260 Crores
Water depth and TD of well: Water depth of the 3D area in this block where Prospect A, B, C and D are to be drilled, falls within the range of 17m to 37m. The depth of wells will be between 2600 to 3000m. Fig. 6: Block Map with tentative prospects. Logistics Details: Name of nearest port: Jafrabad is the nearest port, approximately 53.70 Nautical Miles i.e. 29 Km to the north of the block. Technological Aspects: Drilling: The drilling of the wells is likely to be taken up after submission and MC review of DoC i.e post December 2017. The exploration of these prospects will be upside to the development scheme of MBS051NAA-1 and MBS051NBA-1. Logging: The complete set of logs will be recorded for obtaining information of drilled section. VSP is likely to be planned intermediate as well as at TD in the well.
Cementing: Cementation of Intermediate and production casing will have to be carried out. Cement job will be carried out for isolation of objects and during well abandonment. Casing: The lowering of production casing and testing will depend on interesting hydrocarbon intervals present in the well which will be assessed after drilling the well. Transportation of men and Material: The personnel will be transported mostly by Helicopter service and also by sea route if necessary. Material will also be transported mainly by sea route and also by Helicopter. Duration of operations: The details will be available after the issue of Geo technical order of respective locations by GOG. However, tentatively it may be 4-5 months period for the well.