Real-Time Measurements With Coiled Tubing Increases Treatment Efficiency
Authors: Thomeer H.V. , Willauer D.L. 
Published: October 2008

The use of downhole sensors conveyed on coiled tubing (CT) during well service operations adds value to the job operation. The system allows the real-time measurements of bottomhole pressure (BHP) and bottomhole temperature (BHT), and incorporates a downhole depth locating facility, Surface display and processing equipment allow the downhole data to be presented in a variety of formats and recorded for subsequent analysis. Real-time measurements are used to accurately evaluate reservoir and wellbore conditions prior to, during and following a treatment. During the treatment, reservoir responses are continuously monitored, thereby aIlowing modification of the treatment program to achieve optimal results. Combining the fluid transport and placement capabilities of CT with real-time downhole measurement provides the means to apply precise and controlled treatments. This ability refines the current treatment techniques and provides the facility for development of new well service technology.

INTRODUCTION

In nearly every matrix stimulation treatment, the wellhead pressures and injection rates are recorded. Ideally, these variables should be measured bottomhole.1 The use of CT with real-time downhole measurements has opened the door for increased treatment efficiency. Increased efficiency is achieved by having the single-run capability to evaluate, treat and evaluate the well. The elimination of the uncertainty of computed downhole data allows effective and efficient treatments. Coiled tubing has also been shown to be a more efficient workover method when compared to jointed tubing.2 The use of real-time measurements along with the proper design programs allows a less experienced operator to perform successful jobs, It also allows skilled personnel the ability to optimize in real time and promptly modify the procedure.

The areas where real-time downhole measurements have been observed to be effective are:pressure transient measurements while acidizing to monitor the skin removalpressure transient measurements while lifting a well to determine the skinpressure transient measurements after bullheading the kill fluid in a formation to monitor the shut-in pressuretemperature surveys of producing intervals to determine where acid treatments are neededcasing collar measurements to verify the depth and ensure the correct placement of the plugs or treatment fluids or bothmultiple-zone pressure transient measurements to ensure the proper downhole tool operationpressure transient measurements during the fracturing calibration treatmentstemperature surveys, pressure transient and casing collar measurements to locate the casing leakspressure transient measurements during the well cleanouts to monitor the hydrostatics.

Case studies are presented which demonstrate the advantages of acquiring real-time measured (not calculated or modeled) data. New and existing CT applications can be completed with the degree of accuracy and control that is not achievable using the conventional techniques, e.g., gauges conveyed on wireline or jointed tubing and using surface data to predict downhole data.