What do we mean by Drilling Optimisation? 

 

What is it?  

Drilling optimisation is a term that is frequently heard in the oil industry, but it is not well-defined and so different organisations and companies have their own definitions and approaches.

Typically, the definitions of Drilling Optimisation refer to improving drilling practices and performance; some talk about comparing actual performance against modelled expectations, while others compare to benchmarked performance from offset wells and yet others to trend changes in real-time data. Longsword Consulting regard these as important, but are just parts of the process.

The aim of the optimisation process can also vary; often the intention stated is to increase the instantaneous rate of penetration (ROP), others take a broader view and look to improve the overall rate of penetration.

At first glance, these appear to be the same, however, if the intention is to improve the ROP over a hole section from casing shoe to casing shoe, then this may, in some cases be achieved by reducing the instantaneous ROP and so improve hole cleaning and therefore save time overall on pulling out of hole and running casing.

Companies frequently focus on aspects related to their products and services, for example a bit company concentrating on bit life and ROP, or a MWD/LWD company looking at minimising vibration to avoid damage to the BHA. Both are important, but again they only make up part of the full picture.

 

The Bigger Picture 

Drilling Optimisation is a specialised form of Risk Management. The aim of any drilling optimisation or risk management project is to minimise, monitor, and control the probability and/or impact of unfortunate events (1). For the oil industry, this means reducing the risk of going over budget due to “unforeseen events” and/or poor practices or procedures and of course, avoiding unsafe practices.

Our approach is that the Drilling Optimisation engineer should look at the overall picture and identify where there are inefficient operations that are currently resulting in either non-productive time (NPT) or invisible lost time (ILT). These may be operational such as incorrect drilling parameters resulting in low penetration rates and/or high vibration, they may be process based such as poor connection procedures resulting in premature bit damage, or equipment based such as poor choice of drilling system and bit for the application.

Once identified, cost effective methods of reducing the NPT and ILT must be devised and agreed upon. The improvements then need to be examined to see if they worked as expected and whether there is scope for further improvement. So Drilling Optimisation is a continuous improvement cycle that is intended to reach the technical limit for the well.

The Drilling Optimisation Engineer should be regarded as a generalist in an industry of specialists, they sit somewhere between the worlds of the drilling engineer and the geologist and need to understand both. The engineer needs to approach each problem or study with an open mind and not jump to conclusions without supporting evidence. Each project is different and may involve some or all the following:

•    Identification of optimum parameters to maximise ROP and minimise vibration

•    Control of the ROP to ensure good hole cleaning

•    Ensuring correct procedures are followed for connections, tripping etc.

•    Modifying the bit / BHA design

•    Changes to the well design

•    Geomechanical or pore pressure related issues

•    Rig equipment issues, e.g. are the pumps capable of the flow rates required to clean the hole?

A second question that is frequently heard is “Why do we need drilling optimisation?” or even occasionally “We can’t afford to optimise the operation!” 

In 2008 Spears and Associates estimated that expenditure on drilling and completions exceeded $250 Billion, with rig costs making up 37% or $92.5 Billion of that total. Industry estimates of NPT varied between 15-40% or $14-37 Billion depending on the well type and operator (2).

While the actual dollar values will have changed since 2008, the percentage of the rig costs lost to NPT has almost certainly remained steady and to that needs to be added the cost of invisible lost time.

Reducing both NPT and ILT will impact directly on the bottom line and lead to a quicker return on investment.

In today’s market Drilling Optimisation is not a “nice to have” or a luxury, but an essential part of any drilling program.

 

1.    Hubbard, Douglas (2009). The Failure of Risk Management: Why It's Broken and How to Fix It.

2.    SPE128722, Increasing Efficiencies Through Improved Collaboration and Analysis of Real-Time and Historical Data.