Cement goes digital

A Brazilian combo is hoping to make evaluating cement through tubing less of a headache with its new software.

Samuel Tocalino (left) and Gustavo Longhin.

Trying to assess the integrity of cement behind casing is an ever and increasingly present challenge for the industry, especially as it looks to determine which sections in wells have enough integrity to enable plugging and abandonment operations.

Brazilian firms Adest and SimWorx, based in São Paulo state, have been working together to develop CementFinder software, which could help make this challenge a whole lot easier.

Adest’s founder, Samuel Tocalino, presented the technology, which the partners hope will reach a market readiness level in three years, at the ITF Technology Showcase in Aberdeen earlier this year.

“Until recently, it was common practice to run cement evaluation logs only in the final production casing or liner. Intermediate or surface casing cement isolation was measured by much less precise methods such as pressure indications,” he says.

“To meet modern environmental and safety regulations, the operator of wells to be permanently plugged and abandoned must ensure authorities that all cement isolations are competent, from the hydrocarbon-bearing reservoir to surface aquifers, an indication only possible with dedicated log runs,” Tocalino says. To do this could mean having to remove the production tubing to expose the casing, an operation that requires a rig and the resulting day rates costs. “In wells to be decommissioned, the old production tubing can be corroded or stuck adding more time, cost and hazards to the operation,” adds Tocalino, who worked at Schlumberger for 14 years before founding Adest.

Wave propagation	in a wellbore.

CementFinder is being designed to allow for precise interpretation, in real-time, of data produced from traditional acoustic logs, both in the sonic (cement bond and variable density Logs) and ultrasonic (rotating or radial pad tools) ranges during through-tubing runs.

“In traditional through-casing runs, acoustic wireline tools emit sonic waves and capture the casing returns. Attenuated returns indicate good cement-to-casing bond while strong responses indicate micro-annuli, channelling or absence of cement, i.e., poor hydraulic isolation between different zones,” Tocalino says.

“In through-tubing log runs, the initial and stronger returns are from the free production string reflections followed by noise, a multitude of reflections on multiple surfaces (casing, formation, etc.), still lacking the dedicated examination to be provided by CementFinder.”

CementFinder interprets through-tubing cement log data sets to identify casing reflections within the recorded noise and their attenuation levels indicating the presence of cement and well integrity giving operators and authorities the needed insurance.

“Its development starts with recreating typical wellbore configurations in a computer simulator incorporating variables like acoustic wave properties, multiple tubular strings, eccentricities, cement and fluid densities, background noise, allowing for the precise definition of the casing returns and cement quality indicators in a through-tubing cement log run, i.e., what to look for among the noise,” explains Gustavo Longhin, a co-founder and projects director of SimWorx Engineering Research and Development.

CementFinder illustrated. Images from Adest.

Then powerful noise filters and pattern-search (data mining, association and clustering) algorithms are applied to the log data to identify the expected casing returns and attenuation levels corresponding to adequate isolation or not.

“This approach will lead the way to rigless decommissioning campaigns where CementFinder confirms a good primary cement job and restricts expensive rig operations to the cases where repairs are advised,” Tocalino says.

CementFinder can also be used to measure the cement’s final compressive strength, by combining ultrasonic log data sets with traditional pulsed echo technology.