Enhancing Dynamic Formation Integrity Test and Dynamic Leak Off Test Value Through Effective Wellbore Strengthening and Managed Pressure Drilling
Authors: Ta Quoc Bao , Bui Dung , Xuan Ngoc Nham , Duc Trinh Lai , Van Cuong Nguyen , Ngoc Anh Ta 
Published: August 2024

The pore pressure and fracture gradient profile (PPFG) does not provide a suitable drilling window based on drilling and geological data records of offset wells; a Well Design Engineer may encounter several problems. These issues can be attributed to uncertainties in downhole conditions, and they can lead to unexpected and uncontrolled influxes of formation fluids as well as lost circulation. In order to address these challenges and ensure safe drilling operations in high-pressure, high-temperature (HPHT) environments, advanced technology solutions and hydraulic simulations are essential.

Hydraulic simulation strategies were employed to enhance drilling operations and assess fracture propagation. The Wellbore Strengthening (WBS) software integrates wellbore pressure data, geomechanical characteristics, and specified material parameters to estimate fracture width probabilities. Through numerous analyses and simulations using these variables, the Managed Pressure Drilling software offers insights into the impacts of mud properties, pumping rates, surface back pressure (SBP), bottom hole temperature (BHT), and rotation per minute (RPM) adjustments on the equivalent circulating density (ECD) or equivalent static density (ESD). This data assists drilling engineers in making informed decisions for the accurate application of WBS materials and methods within the formation.

The modified procedure for combining WBS deployment with Managed Pressure Drilling is aimed at improving the safety and efficiency of drilling operations, particularly when dealing with formation fractures, with the goal of increasing the value of the Dynamic Formation Integrity Test (DFIT)/ Dynamic Leak Off Test (DLOT).

Maintain continuous circulation while running the 9 5/8" casing, ensuring that pump rate and bottom hole pressure remained below the fracture pressure. Adjust the mud weight if you encounter significant caving and gas with the maximum allowable mud weight of 1.55 sg before running the 9 5/8" casing. Enhance the DFIT up to 1.72 sg below the casing shoe at 2992 meters measured depth (MD)/ 2500 meters true vertical depth (TVD) using the "Pill Method." Strengthen the formation at 3733 meters MD / 3181 meters TVD with a WBSM Pill. Drill through this weak zone with a mud density of 1.35 sg +/- 0.02 and then increase the mud weight to resume drilling ahead.

Differential sticking and loss circulation issues occurred multiple times while drilling in the 12-1/4", 8-1/2", and 6" sections. Nevertheless, our well-prepared engineering simulations enabled us to successfully manage and resolve these challenges.

The stress cage technique introduces a novel strategy for enhancing wellbore pressure containment (WPC). This approach involves the use of drilling fluids that incorporate carefully calculated engineered particulate lost circulation materials (LCM) to address weak formations. These calculations are conducted in close collaboration with the MPD team to ensure precise placement at the fracture mouth, ultimately contributing to improved well results.