Next generation fluids

The very process of drilling a hole in the earth causes formation damage. It upsets nature’s balance due to tectonic changes around the borehole. Further changes are caused by fluids that wet surfaces, alter chemistry and create emulsions. The drilling process introduces hydraulic forces that are transmitted throughout the borehole and into the formation. Without remedy, these forces cause fluids to invade the rock and create damage that leads to borehole instability and damage that impairs the ability of producing zones to deliver oil and gas to the borehole for production.

The impact on drilling operations can be severe, since borehole instability impairs efficiency of the operation and can lead to expensive remediation or a lost hole. It can also lead to lost production due to reduced flow rates or a well that cannot produce at all. Obviously, any remediation required is expensive and a lost hole is a huge cost, but lost production due to a poorly drilled well can scrap a project. The cost of projects these days is high even before the rig moves on location and the proper, efficient drilling of the well can justify the project and deliver profits. A poorly drilled well is costly to investors and to a world where energy is vital.

Drillers have traditionally dealt with such problems using a combination of drilling fluid techniques and improved drilling practices. The degree of success has varied from very good to limited. Drilling practice is improving and is a result of the changing culture on the rig. Safety is constantly emphasized and drilling practices are a part of overall safety. Once the habit of attention to proper procedures is emphasized and enforced, more efficiency results.

Drilling fluids are more difficult to evaluate and control due to the complexity of demands in many wells. The evolution of drilling fluids is typically that of step changes. One step addresses a certain hole condition, another addresses another challenge and so it goes. Compatibility problems sometimes result or the combination becomes too complicated to control easily. What is needed is to change the way drilling fluids work so that the system being used addresses the wellbore as a whole and prevents problems in a proactive way.

One of the biggest advances is the development of invasion control systems. These systems are designed to work as a fluid, not a combination of products, to minimize the invasion of problem zones. The inherent design of these fluids promotes drilling efficiency and prevents problems such as fluid losses and invasion. These are energized fluids that have the ability to create an at-balance condition in the near wellbore to prevent fluid invasion and damage. Borehole stability is always improved when these issues are addressed.

Field results have been very good. Many drilling problems have been minimized or eliminated, even in areas where such wells could not be successfully drilled with conventional fluids. Drilling, completion, and production efficiency are greatly improved. MWD, LWD and wireline logging efficiency is improved. Drilling days and losses are reduced, casing strings eliminated and cementing results improved. The most valuable success has been the almost immediate production, with easy cleanup and increased production rates.

These fluids have a great deal of future potential and new uses are being explored constantly. An oil-based invasion control system is now in use. The systems (both water and oil) are being used as workover and kill fluids. This is being done in highly sensitive zones where snubbing units are typically used because killing the wells used to damage the zones permanently. Now these fluids are used to kill the well and are put back on production without damage; snubbing units are no longer required.

Work is also being done where the fluids are integrated with other drilling techniques such as underbalanced drilling, managed pressure drilling and in mud-cap drilling. The fluids act to enhance the value of these technologies, widen the window of application and deliver greater value to the operator.

The fluids have demonstrated benefits in other advanced technologies such as coiled tubing drilling, drilling with liner and rotary steerables. These are, in my mind, the ‘next generation fluids’.