Mitigate losses in highly fractured reservoir

The primary oil reservoir of the Mumbai High field is fractured limestone that has been severely depleted since the field was discovered in 1974, making heavy-to-total fluid losses common in this area.

An operator needed to drill an 8 1/2-in HPHT exploratory well near this reservoir. Kicks and partial losses were observed within in the 4.6 ft [1.4 m] between 8,071.85- and 8,076.44-ft [2,460.3- and 2,461.7-m] MD. In the second run, the operator experienced total losses, with a final dynamic loss rate of 80 bbl/h [12.72 m³/h] at 322 galUS/ min [1.22 m³/min] and static losses at 0.5 bbl/h [0.08 m³/h]. The operator needed a way to prevent these losses before continuing.

Use an acid-soluble lost circulation pill to curb losses

After noting the success that the FORM-A-BLOK AS pill had when used previously in wells in the area, M-I SWACO, a Schlumberger company, proposed using the same pill to curb the losses. To make 100 bbl [15.89 m³] of 15.8-lbm/galUS [1,893.26-kg/m³] pill, 35 lbm/bbl [100 kg/m³] FORM-A-BLOK AS pill was added to drill water.

Reduced dynamic losses to zero

After pumping the FORM-A-BLOK AS pill, dynamic losses were eliminated at 250 galUS/min [0.95 m³/min], and the pill was accepted by the operator as a successful solution.