Drilling optimization saves time and eliminates wellbore instability

Overview

Halliburton Project Management (HPM) was tasked with optimizing the drilling performance of Medco Arabia Ltd. in its development drilling campaign in the Karim Small Fields (KSF) region of southern Oman. This project included providing engineering and operational support. A creative and optimized solution was needed to reduce the drilling time and overall well cost. Considerable collaboration with the customer and detailed offset well data analysis would be needed to determine the appropriate solution to meet project requirements at the lowest cost possible.

Challenges

The operational performance of previously drilled wells in the KSF region was affected by a high record of non-productive time (NPT). The majority of this NPT (66.1 percent) was attributed to wellbore instability problems such as tight-hole and stuck-pipe events experienced in an 8 1⁄2-inch hole section. NPT of 143 hours was recorded while tripping out with an 8 1⁄2-inch bottomhole assembly (BHA) in Well “A”. The HPM team would need to analyze data, coordinate with Halliburton product service lines (PSLs), and implement a solution at the lowest cost possible.

Solutions

To optimize drilling performance and reduce overall well costs, the HPM team first performed a detailed offset data analysis. In addition, other Halliburton PSL teams were brought in to analyze the data and offer solutions. An overall collaborative solution was then created.

Drilling engineering software from Halliburton Landmark was utilized to understand the drilling geomechanical events and to calculate the optimum drilling and tripping parameters. The Sperry Drilling Pressure-While-Drilling™ (PWD) tool was used to confirm the hydraulic models and to measure the amount of surge and swab pressure exerted over the formation due to excessive reaming actions. Baroid sized BARACARB® bridging agents were implemented in the drilling fluid system to enhance wellbore stability.

A detailed report was presented to Medco Arabia Ltd., with the following recommendations:

• Changing flow rate and/or pump pressure rapidly could have a bad effect on wellbore stability.
• Considering the colloidal materials (the sized BARACARB bridging agents) in the drilling fluids would help stabilize the wellbore by building the filter cake and filling the induced fracture with the solids to bridge off any fractures.
• Excessive change in pump pressure could have a detrimental effect on the stress and strain of the wellbore, possibly resulting in sloughing. Change in the circulation rate or excessive reaming actions would remove the colloidal materials and increase the sloughing volume.
• Landmark engineering software should be used to establish a torque and drag model prior to any BHA run (especially for highly deviated and horizontal wells). The results should be discussed with the drilling supervisor. The operator should also ensure that the pickup weight, slack-off weight, and rotating off-bottom weight are recorded with every stand, and are used in the model to evaluate the actual hole conditions.
• Reaming down should ensure a cleaner hole, but could also cause unnecessary surges below any packoff or partially packed-off zone. As the hole began to break down in Well “A”, the trip from the bottom of the hole needed to be pumped out slowly without rotation to avoid swabbing and causing further damage to the formations.
• Avoid the whiplash effect as indicated from the time-based drilling parameters.

Results

Through close collaboration with the customer, Halliburton was able to engineer a solution for ultimate drilling performance optimization.

• Various engineering simulations allowed the customer to drill the well 16 percent faster than planned and to successfully overcome the induced wellbore instability problems.
• Landmark drilling software allowed the operator to improve the drilling efficiency and decision making in the KSF region, thus reducing NPT. The average recorded NPT in the KSF region was reduced by 15.2 hours/month (mainly related to logistics) and to zero hours/month (related to wellbore stability).
• The operator saved 8.2 percent of the total well cost after implementing the HPM team’s recommendations.
• No stuck-pipe events were encountered after implementing the HPM team’s drilling and tripping procedures.
• The signs of packoff events measured by the PWD tool allowed the engineering team to calculate and optimize the drilling and tripping procedures.
• The operator was able to run the 7-inch and 4 1⁄2-inch production casing without any downhole problems.