Harsh arctic environment challenges well test operations

Operating in western Siberia, an operator faced multiple logistical and climate challenges in measuring flow rates and sampling fluids of an exploration well located in a harsh and cold environment. Pneumatic control systems in conventional test separators were prone to freezing, and deposits of paraffin inside tubing could affect flow rate stability and compromise the accuracy of flow rate measurements. Equipment delivery was also challenging.

Integrated approach provides alternative to conventional separator

For testing the exploration oil well, Schlumberger designed the well testing equipment package, which normally consists of a heat exchanger, choke manifold, vertical tank, and burner, to include PhaseTester equipment, PhaseSampler equipment, and Vx technology.

Designed for easy deployment, PhaseTester equipment provides flow rate measurements across the life of a field. The Vx multiphase well testing technology used by PhaseTester equipment enhances and improves performance over traditional testing methods. In addition, PhaseSampler equipment provides on-demand information at the wellsite about key fluid properties. Used with PhaseTester equipment, this unique technology enables capturing PVT-quality samples of multiphase fluids at line conditions, directly from the flowline.

This solution enabled the operator to take oil and gas samples under pressure as an alternative to the conventional test separator. Liquid and gas separation was provided by the vertical test tank, from which the gas was taken for burning. Downhole pressure and temperature were measured using high-resolution, high-stability quartz gauges installed in a gauge carrier above the tubing reentry guide.

Solution delivers customer’s well testing objectives

The testing program achieved all customer objectives, including estimation of well productivity, reservoir porosity and permeability, and the sampling of fluids. Four sets of single-phase wellhead samples of oil and gas—under pressure at different flow rates—were taken using this integrated solution.

Because PhaseTester equipment delivers highfrequency measurements that enable real-time monitoring of completion fluid removal, continual flowmeter data monitoring in the customer’s well provided the ability to control flow rates by adjusting the choke to ensure that flow rate and drawdown pressure were maintained within safe limits. Representative measurements of steady-state and transient flow rates were confirmed by comparing data with test tank fluid levels and data interpretation of pressure buildupderivative curves.

In addition, the system provided high-quality and repeatable accuracy of gas flow rate measurements. The GOR measured by the PhaseTester equipment at different flow rates was confirmed by laboratory testing of downhole single-phase samples taken at the minimum flow rates.