Technology in action

The technique of waterflooding as a means to sweep more oil out of reservoir rock pores towards producing wells has been in use for decades. But it has its limits in terms of how much additional oil it can deliver, usually determined either by the nature of the reservoir geology or the economics of pumping large volumes of water at high pressure deep into reservoir formations.

Reservoir rock tends to be heterogeneous, having non-uniform characteristics which can cause unexpected results when water is pumped through it from injection wells. One such effect is that the injected water can flow fast through thin, highly permeable rock layers, in so doing bypassing much of the oil in the reservoir. The water that passes through these so-called 'thief zones' tends to break through to the production wells, and as the resulting hydrostatic pressure builds in the wells, the flow into them from the reservoir can slow down or even stop. While the industry has come up with a number of methods to try to block off the thief zones, such as physical barriers in or near the injection wells, these have proved only partially successful.

What was really needed was a 'smart' solution that would trigger itself automatically when it encountered a thief zone inside the reservoir, diverting the water to the oil-bearing zones of the formation. And a decade ago, inspired by an idea from the company's petroleum engineers, that is precisely what BP began working on in the Prudhoe Bay oil field in Alaska.

In other locations, two treatments were conducted in 2007 in BP's Tangri field in Pakistan - oil production rate was doubled here - and in 2006-8 in six wells in Argentina, where BP is 60 per cent partner in Pan American Energy.

The success rate across the world is high, with additional oil coming from over 80 per cent of the treatments. Further applications are being evaluated by BP for fields in Egypt, Azerbaijan and offshore UK. If, for those fields selected, Bright Water can deliver incremental oil recovery of 1-3 per cent, the net benefit to BP could be more than 500 million barrels of additional oil.

The 'magic potion' envisaged over ten years ago by BP is living up to expectations.

The primary means for keeping individual units and the whole refinery operating optimally is the control loop. This consists of instruments which measure parameters in the process units such as flowrates, temperatures and pressures, and use the data to adjust the setting of associated control valves in the loop in order to maintain the desired conditions in the process units. These controlling mechanisms lie at the heart of achieving the exacting specifications demanded for refined products, and also help to ensure that safety standards, equipment limits and environmental regulations are met.

A typical refinery requires well over 1000 control loops to operate it effectively. But ensuring every loop is performing at its best is a challenge - loops need to be 'tuned' correctly, they can become unstable, valves can be sized wrongly or can stick. For these and other reasons, control loops can actually introduce unwanted variability into unit operations.

Traditionally, process and process control engineers have relied on manual methods to identify poorly performing control loops, diagnosing the causes in response to operational issues as they arise - a time consuming, iterative and often difficult task. But now, BP is applying sophisticated software to the problem which is already having a positive impact at the company's many refineries around the world.

The refineries are benefiting in several ways from the software systems. For instance, Texas City and Whiting refineries in the USA have been able to identify control loops that were in 'manual' mode rather than in 'automatic' mode as originally designed, thereby helping to enhance safety and environmental operations. In BP's refineries in Germany and Spain, the plants are focused on optimising performance. BP Germany has reported that the use of PlantTriage helped accelerate unit startup activities in 2008, by identifying a malfunctioning level sensor associated with a crude unit stripper and detecting several control valves that were oscillating.

While each instance of improving the performance of a control loop may seem small in isolation, taken together they paint a different picture - BP's refineries estimate that benefits of the order of $1-5 million per year are being realised in each refinery by deploying the technology and understanding how to use it to full advantage.

Corrosion monitoring is of particular importance in deepwater projects where pipelines sit out of sight on the seabed, often in several thousands of metres of water, carrying hydrocarbon fluids at high pressures and temperatures. Conventional techniques for effectively monitoring localised corrosion have limitations - either due to high pressures or temperatures inside the pipe, or by being unable to produce results with sufficiently high resolution or within a short timescale.

Cormon's now-patented technology is known as RPCM - ring probe corrosion monitor - and uses an enhanced form of the established high-sensitivity electrical resistance (ER) method to measure metal loss.

RPCM takes the technique used in standard ER corrosion probes and applies this in an innovative ring configuration to enable 360° monitoring in a pipeline, compared with conventional single point monitoring. The rings are made from the same carbon steel material as the pipeline and are the same diameter, and sit in the line within a welded spool (see graphic below), enabling full fluid flow to pass through the line unimpeded, as can conventional pipeline 'pigs' used for cleaning and inspection.

The rings in the spool are machined into identical pairs - three pairs are typical - arranged such that one ring in the pair is exposed to the fluid flow while the other is a ceramic coated, isolated reference ring.