A Subsea Multilateral Oil Producer, Completed with AICD Sand Screens and Selective Inflow Valves is Evaluated by Combined Acoustic and PL Tools, Identifying the Sand Producing Branch and a Tubing Leak in a Single Operation

Abstract

Abstract Subsea completions offer a number of advantages, but intervention operations can be complex and expensive. A horizontally completed multilateral well exhibited unexpected sand production and a tubing leak leading to the well being shut in. This paper discusses the novel tools and techniques deployed to localise the tubing leak, identify the bore responsible for sand production and to provide relative sand quantification at differing flowrates The evaluation methodology was essentially the same as a comprehensive production logging intervention, with the addition of a novel acoustic tool to quantify sand impacts. Data was recorded with the tools stationary while the well was flowed in a variety of different states by means of hydraulically actuated inflow control valves. This enabled well behaviour during transition from one state to another to be monitored in real-time and recorded, giving unprecedented insight into sand production dynamics, as well as sustained production from stabilised flowrates. Logging at different flowrates at different depths allowed quantification of minimum sand transport flowrates. With the well shut-in, a leak detection survey was conducted while running in hole and a faulty GLV identified. With the well flowing comingled from both mainbore and lateral 2, data indicated a mixture of oil and water being produced, along with significant quantities of sand. Choking back both bores to 50% resulted in continued water and sand production. When the ICV was cycled to close lateral 2, water cut and sand production both increased with slug flow evident indicating the mainbore was producing sand associated with water production. Lateral 2 was then reopened and the mainbore closed. Sand production declined to zero and the water cut dropped, showing that lateral 2 was not producing either sand or meaningful amounts of water. The time-based data was recorded at depths, one in 3-1/2" tubing above the ICV and the other in 5-1/2" tubing higher up. For a given flow rate, it was possible to compare relative sand rates at the 2 points and infer the fluid velocities needed for sand transport to occur. The data identified the source of the sanding, the source of the water and the minimum flow needed to prevent sand settling in the well. Robust and reliable detection of the presence of sand in 3-phase production flow is a powerful tool in itself to allow diagnosis of failures of sand control, in this case the positive identification of the bore responsible for sand production. The addition of a quantifiable fourth phase to traditional production logging elevates the understanding of downhole sand production by enabling the correlation of sand rate with variable parameters such as holdup and local fluid velocities.