Downhole tool failures induced by drill string vibrations was one of the leading causes of non-productive time in a deep exploratory field in southern Iraq. To improve drilling efficiency, it was paramount to understand the primary source of potential drilling dysfunction before commencing field development phase. To overcome the challenge, a finite element analysis (FEA) study was developed to simulate the drillstring transient dynamic behavior from bit back to surface. The model has been utilized to quantify the potential vibration, contact force, torque, displacement and other high-interest parameters of every drillstring component in the wellbore. To fully exploit the modeling algorithms, it is required to input a comprehensive dataset including mechanical rock properties, cutting structure design, bit drive mechanism, drillstring physical characteristics, 3D well profile and expected drilling parameters. Using offset well data, surface and downhole measurements, and a thorough knowledge of drilling equipment, the model creates a virtual drilling environment simulating the downhole drilling conditions enabling the evaluation of the source of inefficiency. Finally, the model is validated for its accuracy by comparing its outcomes with actual field acquired data. By accurately modeling the drillsting interaction with the drilling environment, the operating company was able to evaluate different BHA options to safely drill the wells and by reducing harmful vibrations, minimizing tool failures, increasing ROP, this translates to a reduction of drilling time by 24%. This paper will share with the industry a case study demonstrating the value of the utilization of the advanced dynamic modeling which has been able to save over 500 K$ per well to the operating company by an efficient selection and placement of drill string components. This approach has enabled to outperform past drilling performance and has become the norm in similar fields in southern Iraq.

Obtaining a good cement bond is a continuous challenge, especially if the well being cemented is a high-pressure exploration gas well, and it is one of the very few gas wells drilled in the country. Poor adherence to the casing and the formation, channeling due to gas migration and microannulus are some of the main risks that could result in a poor cement job. Achieving zonal isolation and a good cement sheath protecting the 7-inch liner turned out to be an objective missed for the first two wells of the campaign, compromising the long-term supply of gas to the South region of Iraq. To solve the situation, it was necessary to implement something more than a mere cementing additive; it required a multifactor analysis with an experienced multidisciplinary team. A set of good drilling practices, proper drilling fluids, proven cementing techniques and new technology slurries were combined to improve the precious results. To obtain a sound cement quality log, the well engineering department teamed up with cementing experts, drilling fluids specialists, liner hanger company representatives and operations personnel. With effective meetings, proper risk assessment and visible leadership, the team generated a series of initiatives that included: drilling hydraulics optimization, mud weight selection, drilling practices re-definition, liner hanger procedure adjustments and cementing slurry design. As a result, the borehole caliper was significantly improved, the liner hanger allowed full rotation while cementing, cement returns were observed above the liner top after the job, no evidence of gas migration was observed and the CBL-VDL-USIT log showed a remarkable improvement in the two jobs where the engineering initiatives were applied. Being able to achieve a positive proof on cementing integrity, one of the most important acceptance criteria for the National Oil Company (NOC) regulation entity, enhanced the trust on the technical experts of the engineering team to deliver solutions of complex problems.