Deepest Section Drilled Successfully to TD Using an Advanced Air/Foam System in Highly Fractured Formations of Cretaceous Age in Sulaiman Fold Belt, Pakistan – A Case History

Abstract

This paper reviews the case history of the deepest section drilled using a specially designed air/foam system in the highly fractured carbonates of "Fort Munro & "Parh" in Kup well-1 located in the Sulaiman Fold belt of Pakistan. These carbonates presented numerous drilling challenges in the well. While drilling with a conventional mud system, total incurable losses were encountered. The client attempted to cure losses by conventional means of LCM pills and cement plugs but total losses were continually encountered after drilling just a few meters with conventional drilling fluid. To address the tedious problem of lost circulation, a design of an advanced air/foam system was considered to be used for further drilling.

The paper starts off by discussing the challenges associated with drilling such a deep section with an air/foam system, and how an advanced and more sustainable foam system was designed. Numerous challenges were associated with designing a foam system for the subject well. First; the depth of the section was till 2300 m which would require a foam system to be able to bear its own hydrostatic head, second was the higher than normal formation temperature of 225 deg F which would drastically harm foam quality, and the third & last was that the designed foam system would be able to clean the hole properly at higher drilling rates compared to conventional drilling. The paper will then also present the methodology for job execution and finish off with the delivered results and conclusions.

To summarize, an advanced air/foam system was designed to mitigate total loss of circulation encountered in these carbonates of cretaceous age in Sulaiman Fold Belt of Pakistan. The advanced air/foam system allowed the operator to drill that part of the well to desired depth and successfully cased the troublesome formations. Besides curing the total losses in the subject formations, the operator was able to achieve an ROP which was five times the ROP compared to conventional drilling in the same formations. This paper will highlight the design process used to devise an advanced air/foam system that enabled to drill these carbonates of "Fort Munro" and "Parh" formations in the well. The paper will be targeted towards presenting the design objectives, the onsite execution, and the lessons learned in developing an advanced air/foam system for the well. This will aide in the efficient designing of operations for upcoming wells with similar problems even anywhere else.