Schlumberger

Performance Report: Critical Deepwater Frac-Pack Recovery and Successful Workover Attributed to DIPRO System

Challenge: The highly faulted and compartmentalized field consists of geo‐pressured, unconsolidated silt/very fine sand Pleistocene‐age reservoirs. Cased‐hole, frac‐pack completions are used on all wells in this field to maximize well productivity with minimum solids production. Shunt tubes have been installed with the gravel‐pack screens to help ensure proppant placement in the casing/screen annulus over the entire reservoir interval. The third well in a series of completions was frac‐packed and completed in the same manner as the first two successful completions—a premium laminated screen on 3.5‐in. (89‐mm) outside diameter, 9.2 lb/ft base pipe with two shunt tubes placed across the perforated interval. The gravel‐pack screen failed at the beginning of production due to excessive production rate and drawdown. The well was shut in. Coiled‐tubing operations to remove the gravel and screen from the well proved unsuccessful.

Solution: After conferring with the operator and field participants, M‐I SWACO engineers specified the fluid requirements to carry solids and debris to the surface at low pump rates and to control whole fluid loss to the formation with an overall objective to recover the gravel‐pack screen, re‐perforate and re‐complete the well. A 12.8‐lb/gal (1534‐kg/m3) DIPRO fluid was recommended to control losses to the formation through open perforations, as well as washover the screen and remove the frac‐pack proppant.

Result: Total losses of DIPRO fluid to the formation were 41 bbl after 25 days of exposure to the formation. The brine‐base drill‐in fluid was used to wash over 225 ft (69 m) of blank sand screen in 13 hr (two trips) with minimal fluid loss and no sweeps required. A short period of lost circulation (35 bbl to regain full circulation) was experienced while washing over the screens near the suspected screen failure depth. After washing over the screens down to the sump packer, the screens and shunt tubes were retrieved fully intact. One shunt tube was packed with formation sand. The outer layer of screen was packed with filter cake and a greater than 2‐in. (51‐mm) diameter hole was observed in the premium screen adjacent to an end ring. The well was successfully re‐perforated and re‐completed.

Well Information
Location Garden Banks, Gulf of Mexico
Well deviation 36.44 degrees
Perforated intervals Total of 130 ft (40 m) from 15,354 to 15,494 ft (4680 to 4722 m) measured depth
Perforated intervals 106 ft (32 m) from 14,996 to 15,102 ft (4571 to 4603 m) total vertical depth
Density required 12.8 lb/gal
Bottomhole temperature 146°F (63°C)
Completion type Cased‐hole, frac‐pack

Productlb/bbl
12.5‐lb/gal CaC12/CaBr2
DI‐TROL 8.00
DI‐BALANCE 0.50
SAFE‐CARB 2 4.00
SAFE‐CARB 20 15.00
SAFE‐CARB 40 9.00

After the well was killed with 12.8‐lb/gal (1534‐kg/m3) calcium chloride/calcium bromide blend and tubing and control lines were recovered, the blend was displaced with 12.8‐lb/gal (1534‐kg/m3) DIPRO fluid. With the approach of the first hurricane, the rig was evacuated for six days. The fluid system maintained its pre‐storm properties and was used to wash over and recover the gravel‐pack assembly.

To retrieve the screen a 3‐bbl/min wash rate was required. On the workover well, this equated to 300 ft/min (91 m/min) annular velocity for the screen‐by‐washpipe annulus and 950 ft/min (289 m/min) annular velocity for the washpipe‐by‐casing annulus. A high torque rate was experienced during washover operations and the washpipe was rotated at 40 to 50 rpm during the entire wash as any added torque would have increased the risk of damaging the screens or leaving washpipe in the hole.

With the approach of a second hurricane, the rig was evacuated for four days. The DIPRO system again maintained its pre‐storm properties. The well was displaced to the 12.8‐lb/gal (1534‐kg/m3) brine before re‐perforating and completing the well.


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“Not only did completions in this deepwater development challenge technical skill, two hurricanes interrupted operations. The DIPRO system delivered remarkable performance even after 25 days of exposure to the formation.”
John Carboni
Project Engineer
M‐I SWACO