Water management

In Search of Cheap, Fast Ways To Detect Water Troubles

Treating produced water to control bacteria is like weeding a garden. It addresses the problem that is not going away.

A researcher at Texas A&M Engineering Experiment Station (TEES) prepares samples of produced water for bacterial analysis using the Bactiquant test from Mycometer.
Source: TEES

Treating produced water to control bacteria is like weeding a garden. It addresses the problem that is not going away.

Regular field testing shows water quality is highly variable. The biological and chemical makeup of a tank of produced water is complex and can quickly change as water from other sources is added and microbes rapidly multiply.

“In the Permian Basin, I went out to wells that have been recently fractured and within 2 months they are already soured. It was back-traced to poor water quality. That happens more often than you think it does,” said David Burnett, a research scientist at the Texas A&M Engineering Experiment Station (TEES).

One of the TEES projects is seeking practical, cheap, reliable, and quick testing options for microbes and chemicals, and seeing if those tests also work in the hands of a worker in the field. The goal is to convince operators that they need to test often and can rely on those results to manage their operations because performing a test that costs USD 10 or less could save USD 500,000 on a workover.

TEES’ interest coincides with a spate of new options on the market for biological and chemical monitoring of oilfield water.

One that met TEES’ criteria when tested is made by Retego Labs. The Internet-linked screening equipment has been provided to oilfield service companies to vet their screening methodology for chemical, mineral, and microbial content. The test usually takes less than 3 minutes, and requires adding a 3-ml sample to a test vial that contains the chemicals needed for a portable unit to measure a specific target. No pretreatment of the sample is required, and the cost is less than USD 5 per parameter tested.

Test Gap

The “stability of treated water during storage has not yet been explored due to the difficulty of obtaining timely and accurate microbial levels,” wrote Allana Robertson, a recent Texas A&M graduate, in a paper. She reported on the use of a variety of test methods showing that “treated produced water still exhibits an unstable nutrient-rich nature capable of supporting microbial growth.”

“Without the addition of a biocide to establish a residual concentration, microbial biomass levels can be expected to regrow surprisingly fast after any removal treatment,” Robertson wrote.

The high cost of biocides, and regulations on how much can be used, limit them as a long-term control option. And bacteria can multiply faster than traditional lab testing services can deliver results.

“A lab could take 2 to 3 weeks to get results back and by then it is too little, too late,” Burnett said, adding, “It was a breakthrough when we found something that can work in hours rather than days.”

Robertson’s paper and Burnett’s testing program are aimed at convincing industry that there is a need, and the tools are available, to accurately measure the quality of a costly resource. The results in the paper included tests using the Bactiquant water meter that TEES is evaluating as a better alternative to long-established approaches to microbe monitoring.

Portable testing equipment makers are facing limited competition. Few commercial labs will test produced water, which is a complex brew capable of killing costly lab equipment.

“Private environmental labs are generally set up to test industrial waste and municipal waste water. But when companies start bringing in water from fracturing and flowback, they are generally not set up” to handle it, said Keith McElroy, a consulting microbiologist and produced water treatment expert at TEES.

There are no formal industry standards for the testing of oilfield water. It is up to operators to know what they are looking for.

“They know how to do it. But they ask what you want to test and you are back on square one. The operator doesn’t know what he wants to test. What is critical?” said Burnett, whose projects include seeking an answer for that question.

TEES has found that some tests proven in other industries are a bad choice in an oil field. Some are physically impossible to do—for example, a test based on the observation of a change in color of a fluid is not going to work when the water is black, McElroy said. Other tests require skills not likely to be found on a drilling crew, such as ensuring that samples are collected in uncontaminated glassware, and that the samples collected are representative of the water to be tested.

Burnett describes the challenge this way: “It is a 10-million-gallon job and they are pumping 80 bbl/min, and a guy with a test tube is trying to grab a sample.”