Description

Wellbore stability is the main issue for most of drilling area. There are many types of formation has high risk for stability. Salt formation can be the most dangerous one. An oil base drilling fluid systems is usually the only option for salt drilling, because of its stability and minimum reaction with salt. On the other hand, due to high cost, the oil based systems can not be an option. A water based super saturated salt saturated polymer drilling fluid provided stability and performance in a very challenging environment. The case has a high core recovery record among the area.

Challenges and Problems:

* Anhydrate contamination above salt formation

* Active clay above salt formation

* Wellbore instability above salt formation and in salt formation

* Stability in salt saturation, which can alter due to crystallization with the increase in bottom hole temp.

* Hole geometry in salt formation

* Coring operation; highest recovery target.

Challenges and Solutions:

When it was necessary mud weight was increased to sustain wellbore stability. At 12 ¼ in section MW was increased up to 11.40 ppg due to drilling and salt addition to saturate mud. So that, wellbore was kept stable and with a minor contamination from anhydrate formation. Controlled API fluid loss under 5.0 cc/30 min during section. KCl, the main inhibition provider with the help of REOPAC LV, resulted to in gauge hole and minimum tipping problem. And no issue was observed due to the active clays. Started 8 ½ in section at 11.40 ppg MW and it was up to 12.50 ppg due to drilling and barite addition to mud. Controlled API fluid loss under 5.0 cc/30 min during section.

Slat formation erosion due to salt solubility in water-base mud. To minimize salt formation solution in drilling fluids,chloride content of the fluid was monitored and controlled at high temperatures.