Upstream oil and gas operators are continuously challenged to find the safest and most cost-effective ways to remotely access and visualize real-time data from offshore wells. Traditionally, upstream oil and gas production engineers have reacted to challenges in their wells by procuring WRFM1 temperature 2 1 WRFM – A term used in the oil and gas industry for Wells Reservoirs and Facilities Management surveillance data to help them make decisions that will yield the highest value. However, these services increase the risk to the workforce, increase operational costs, and defer revenues from production by taking the well offline. Enter fiber optics — this technology enables temperature data to be read continuously.
Fiber feels the heat (and the cold!)
Fiber-optics technology (or ‘fiber’) continuously provides temperature surveillance data along the full depth of the wellbore, enabling oil and gas operators to avoid the use of a temperature Production Logging Tool (PLT) service. A PLT can be used to measure wellbore flow and wellbore temperature while a well is offline. The use of PLTs increase the safety risk to personnel as it requires them to open up the well to lower and raise the tool. This also adds operational expense and production deferment.
A single fiber-optic cable, thinner than a human hair, gathers the data that thousands of highly accurate temperature sensors would gather along the depth of a well, at a fraction of the cost of existing technologies. No downhole moving parts or electronics are needed. A light box located on the surface transmits brief pulses of laser light into the fiber. Changes in temperature downhole slightly deform the fiber and modify the returning light pulse. These deformations essentially turn a fiber into temperature sensors that are separated by a few feet (e.g., three feet is typical) along the full depth of the well. This provides near real-time WRFM surveillance without downhole moving parts or downhole electronics.
The use of fiber is enabling upstream businesses to minimize personnel risk, costs and production loss by keeping the well online. Although the technology started being applied in the 1990s, it Figure 1: A typical deep water fiber optic installation is now becoming more mainstream. Three tangible fiber success stories:
- The US government regulatory agency required an operator to provide justification of well integrity to keep production online. The company calculated thermal pressure changes in the upper and lower annulus using historical temperature profiles measured from the fiber. They then provided well integrity documentation and obtained approval to keep the well online, protecting over $200 million in revenue.
- An operations manager wanted to increase production safely after a water breakthrough. The production engineer confirmed that a ramp -up of production could safely occur by using the historical temperature profiles from the fiber which validated that high-end temperatures had not been exceeded. They then used real-time temperature profiles as a calibration point while safely increasing production to historically high levels, generating an additional $20 million in revenue.
- A production engineer needed to determine if a malfunctioning gas lift valve was the cause of poor production. He used the temperature profiles to confirm the gas lift valve was functioning properly, confirming the fluid level was below the deepest gas lift valve. He was able to avoid the need to run a PLT for this purpose. This minimized the safety risk by involving a fewer number of employees and reduced operational spending by $300,000.