Drilling rate at the technical limit

Recorded drilling times may show significant variations from one well to another even for the same total drilling depth, in the same field. Apart from the formation properties, drilling engineers’ technical ability plays a significant role in required drilling time. Comparison of drilling performance with respect to previously drilled drilling records is a common technique applied to assess if there is any need for an improvement.

A graphical technique, known as ‘learning curve analysis’, is widely applied for performance evaluation. This approach has two major drawbacks. One, there may not be adequate number of drilled wells to make a healthy comparison. This is often the case in a newly developed field. Two, past drilling practices could be performed with bad engineering practices. In such a case, comparison of a given drilling performance with respect to bad engineering practices does not necessarily prove that the current practice represents a good performance. This is usually the case where previously drilled wells were carried out by inexperienced drillers and/or with old drilling technology.

In this paper, a different approach is introduced to assess drilling performance, and to alleviate the problems of learning curve analysis. The new approach suggests that the drilling rate is compared with a newly introduced parameter, called as drilling rate technical limit. It will be defined as the maximum achievable drilling rate without risking drilling safety. This method is superior to learning curve analysis because; one, it does not depend on the previous drilling records, two, it aims to drill a well at the fastest rate possible without jeopardizing the safety of drilling operation. It has a couple of disadvantages; one, the proposed method can only compare the drilling rates, two, it is laborious.

The new method calls for the assessment of the operational values that will maximize the drilling rate. Afterwards, it requires the quantification of drilling rate by one of the popular penetration rate models. This paper explains how to assess the most favorable values of key drilling parameters, so that the drilling rate can be maximized. This calls for the simultaneous consideration of drilling parameters’ mathematical relationship with potential failures, as well as their mathematical relationship with the drilling rate