Cointerpretation of Distributed Acoustic and Temperature Sensing for Inflow Profiling
Authors: Carpenter Chris 
Published: June 2017

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 180465, “Cointerpretation of Distributed Acoustic and Temperature Sensing for Improved Smart-Well Inflow Profiling,” by Ahmed Bukhamsin and Roland Horne, Stanford University, prepared for the 2016 SPE Western Regional Meeting, Anchorage, 23–26 May. The paper has not been peer reviewed.

With the availability of more-complex smart-well instrumentation, immediate evaluation of the well response is possible as changes in the reservoir or well occur. Most current work in distributed measurements looks at distributed-acoustic-sensing (DAS) or distributed-temperature-sensing (DTS) data individually, which limits inferences about multiphase-flow problems. The objective of this work was to look at these two types of data together and determine what improvements can be achieved in multiphase-flow problems compared with the conventional methods of looking at DAS and DTS alone.

Introduction

Two prominent tools that provide compartmental-monitoring and control capabilities of horizontal wells are fiber-optic distributed measurements and inflow-control valves (ICVs). The combination of both tools provides an opportunity to adjust well production by choking valves on the basis of observations made in real time, to hinder production of unfavorable fluids. Changing downhole conditions provide new production data, and this management loop can be closed with an effective production-optimization algorithm.

In this paper, the authors present the basic procedure to use DAS measurements for inflow profiling. The analysis encompasses calculation of fluid-flow rate and fluid composition. The current profiling algorithm is limited to analyzing a two-phase fluid mixture.

The complete paper contains a detailed discussion of the theory behind new aspects of the analysis and summarizes the DAS flow-profiling procedure.

Example—Inflow Profiling With DAS

Well A produces single-phase oil because it is operating above the bubblepoint pressure with no water. The well has a cased-hole completion with junctions that connect it to two laterals and a main bore. The main bore and laterals were left open hole to allow flow from their whole length. Three ICVs were installed in the well to control inflow from each lateral. The fiber line was run along the annulus between the tubing and casing. The three ICVs provide the operator with the capability to run different production scenarios to study the effect of changing an ICV position. Three different production scenarios were analyzed, with fully open, half-open, and fully closed valves. Once a new valve setting had been applied to the well, DAS data were collected for 3 minutes after the surface flowmeter had shown a stabilized flow.

Acoustic data were segmented into several blocks to calculate the speed of sound at that instance in time and at that particular depth. The overall procedure starts from well-data collection until a flow-rate measurement from the well is acquired. For each time/depth block, the 2D Fourier transform is applied. Then, the speed-of-sound line is fitted by finding the maximum integral value. The result for a block is inserted into a speed-of-sound table before moving to the next block.