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Depletion Pattern and Extent in TS6 Pay Sand of Lakwa Field, Block-6 as Revealed by Well Logs and Production Data

Ashok Kumar, Yogesh Chandra, Jai Pal Singh, and D. Ramachandra Rao
Well Logging Services, Assam Asset,ONGC, Nazira, India

Lakwa field, located in Upper Assam, India has multiple pay sands of Eocene to Miocene age. The field was discovered in 1963, and the production commenced in 1968. Some of the pay sands producing for last four decades have undergone depletion with drastically reduced production. TS6 in Block-6 is one such pay sand. It is an elongated pool formed against a sealing fault with maximum gross pay thickness of 46m and porosity 16 to 19%. It has initial oil water contact and bottom water drive mechanism. The pool is penetrated by total 30 wells, and exploited through total 16 wells in different time spans. At present, only two wells are flowing; the rest ceased due to high water cut.

In a recent study carried out primarily for rejuvenation of non flowing wells, an attempt has been made to know the depletion pattern, extent of depletion and rise of oil water contact etc. with the help of existing well logs and production data. The OWC-Time plot, bubble plot and composite log triplets of old, intermediate and new nearby wells have been prepared and analyzed along with production data. The analysis has shown both vertical and horizontal movement of water. The data integration and analysis have helped to know the depleted areas, extent of depletion and overall current status of the pay sand enabling appropriate decision on non flowing wells. The flowing wells have also been analyzed. Well positions and preferential water movement are recognized as the main factors behind sustenance of the flowing wells.

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