Depleted reservoir pressures, problematic BCS section, frequent stuck-up formation damage and environment conditions in Upper Assam today, need Polymer based mud to improve the efficiency and effectiveness of drilling operations, to minimize formation damage and ensure maximum production from depleted reservoirs.

Conventionally polymer based mud is used in 8.5 " section against problematic BCS section and deeper producing horizons BMS, Kopili etc. The mud used in earlier phases is disposed off / thrown to the waste pit. Throwing / disposing of mud is a great problem in Upper Assam because of environmental constraints.

An innovative approach has been developed which is not only environment friendly but cost effective too. Lime flocculated and Low lime mud system were used previously to drill down Girujan clay and against (Tipam, BCS, and BMS) respectively.

Under the new approach. Bentonite content is gradually reduced and substantiated with Guar-Gum and XC-Polymer. Lime (Ca++ ions) have been replaced by K+ ions and KC1 flocculated mud system is run in place of Lime flocculated upto Girujan clay. 3 - 5 % KC1 is introduced during drilling Tipam sands to maintain the porosity and permeability intact. The system is fully converted into KCl-Polymcr system against BCS, BMS, and below having 2 - 3 % Bentonite, 3-5 % KC1, 0.1 - 0.2 % XC polymer, 0.2 - 0.3 % PHPA and 0.5 - 1.0 % PAC. Many wells in Gelekey, lakwa and RDS have been drilled successfully with this approach. Thus the approach will fulfill the objective of using polymer based mud without harming the environment.

Polymer base mud in Upper Assam project of ERBC is used because of the following reasons:

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