Drilling Fluid Losses

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Drilling fluid losses are undesired drilling events, which add complexity to well control, cementing jobs and completion operations. Curing fluid losses is time-consuming and increases well AFE dramatically.
TGT’s Spectral Fluid Losses services (SPEC-FL*) locate the lost circulation zone and determine effective flow loss, allowing our Customers to optimise mud weight, drilling hydraulics and other parameters to regain well control.

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Problem:

The well was under drilling when sudden losses occurred. During an attempt to control the losses by adjusting mud weight, a high H2S gas kick occurred in the shallow sections of the reservoir. Although the operator controlled the gas kick by adjusting the mud weight, the losses continued for several weeks. Despite the operator’s attempts to adjust mud parameters, the well was unstable. Numerous LCM pills were pumped into the bottom of the interval, dramatically increasing the cost of drilling fluids and chemicals as well as AFE due to unexpected additional rig and services costs.

Diagnosis:

TGT was requested to perform a Spectral Fluid Loss survey (SPEC-FL) to pin-point the losses and their effective flow interval. A SPEC-FL* survey, a combination of high-precision temperature logging and high-definition spectral noise logging, was conducted through the drilling string during the drilling loss period.

Findings:

The recorded log showed that the losses occurred not at the bottom of the drilling sting, as the client expected, but several hundred metres higher. In addition to the fact that they were not in the expected formation, the log indicated four long intervals in which the losses had two components: a fracture component associated with low-frequency noise generated by fluid loss through fractures and a rock matrix component associated with high-frequency noise. In addition, the effective flow interval of the losses was determined.

Actions:

Once TGT pin-pointed the loss interval and determined the effective height of formation fluid inflow, the operator initiated a focalised LCM treatment in the areas identified by the log. Afterwards, TGT recorded a second log to determine the effectiveness of the treatment. The findings showed that the losses in units A1 and A2 have been controlled. At the same time, TGT found out that the matrix component of the flow losses in units A3 and A4 has also been cured. Due to the criticality of the well and to safely regain well control, the operator decided to add a second LCM treatment using different LCM in the remaining areas with A3 and A4. TGT re-surveyed the well and concluded that A4 losses have been cured and the major component of losses associated with the fractures in A3 has been mostly controlled.
June, 2016