Drilling efficiency is an often used term for various measures that purport to represent the relative difference between current performance and some reference performance. Non Productive Time (NPT) is globally used as an analogue for efficiency. Many reported efficiency measurements are in the 90% range and NPT in the 20% range when the overall drilling and completion times are some 50% or more slower than Best In Class (BIC) as determined by external benchmarking. Current measures of drilling efficiency and NPT are both misleading and poorly defined.

This paper evaluates these misleading measurements and introduces the application of a meaningful measure of drilling efficiency. The term drilling efficiency is used for a short description; the same process applies to all well operations including drilling, testing, completion, well intervention, workover and plug and abandonment operations; the well life cycle.

Means to estimate overall performance potential including Technical Limit (TL), Maximum Theoretical Performance (MTP) and benchmarking are explained in their historical context and current applications. These provide the future state target for gap analysis to current state performance. This gap allows the quantification of Invisible Lost Time (ILT) whose reduction is the means to true performance improvement over deficiency correction as measured by NPT. ILT commonly gets included in Productive Time (PT) as logged in daily report data-base systems and will remain invisible without such a gap analysis. It is a more important measure of performance efficiency than both NPT and the often used ‘uptime’ of a drilling rig.

Measurements of industrial process (construction, manufacturing) efficiency are presented and, through analogy, applied to drilling. The result is a robust methodology for the industry to measure drilling efficiency.

This paper also includes a review of and suggestions for a normalization index for the relative complexity of various drilling operations ( Appendix I). A simple and comprehensive well complexity index methodology that can be applied to adjust the calculated MTP for any well to develop a calculation based Technical Limit will benefit the industry. An industry approach to establish a defined well complexity index for universal application to drilling is suggested.

A drilling efficiency model with reference to a calculation method is available for the industry to measure the real gap to 100% efficiency. This will in general produce vastly lower efficiency numbers for current performance than some of the inappropriate efficiency calculations currently used. It provides organizations with a more accurate view of the improvement potential they could aspire to reach, and become an enabler for the global oil and gas industry to improve performance and reduce cost of wells.

The recommended methodologies and efficiency measure provides the first realistic number for drilling efficiency. It will be a wake-up call to the industry and initially show much lower efficiency numbers than many organizations currently calculate and report. It will be an eye opener to managers who want to truly assess the performance of their drilling operations and provide them the information to set new performance goals. The challenge will be how willing the managers are to show how badly we perform as an industry today, and how persistent they are in the needed step change and follow through with improvement steps.

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