An operator experienced severe lost circulation while drilling through several troublesome formations in Walker County, Texas. These formations include: Wilcox, Midway, Woodbine, Austin Chalk and Buda. The operator lost over 12,000 barrels of oil-based mud on an offset well and experienced costly non-productive time (NPT). Controlling the losses with conventional lost circulation material, squeeze pills and other techniques were ineffective and resulted in subsequent wellbore instability.
On the next well, which was a direct offset, the operator applied a preventative and proactive approach. This operator has a long history of utilizing Impact’s STAR SHIELD® wellbore shielding® technology and realized they were encountering varying wellbore instability culprits, ranging from pre-existing natural fractures to mud weight induced lost circulation by significant formation depletion. To address the broad range of wellbore instability, the operator took a strategic, preventative approach to limit the following issues:
-Mud weight induced lost circulation
-Whole mud losses to preexisting microfractures that varied in sizes greater than 250 micron fracture width and less than 3000 micron fracture width
The operator treated the entire active circulating system with 5 lb/bbl STAR SHIELD and 5 lb/bbl of STAR SHIELD 500 for preventative management. Next, they prepared and made ready at all times a 40 bbl, 40 lb/bbl STAR SHIELD 3000 pill to quickly pump and seal any preexisting fractures greater that 500 micron. Realizing that a critical means of dealing with large, pre-existing fractures requires operational awareness and readiness to promptly seal the fractures before the fracture tip has an opportunity to extend and establish connectivity with other fractures.
The combination of the STAR SHIELD product line reduced mud losses by over 90%. The operator described the tactical approach of utilizing the STAR SHIELD product line as very successful in preventing major mud losses to the formation and subsequent NPT. The operator continues to utilize this Wellbore Shielding® technology process with great success in other regions.