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This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper URTeC 3719030, “Not Measured, Not Improved: Agile Three-Phase Well-Flow-Measurement and Well-Testing Unit,” by Bali Singh and Bruce Gerrard, SPE, Apache, and David Reasoner, SPE, NeoTek Energy, et al. The paper has not been peer reviewed.

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The complete paper highlights well-test challenges, provides an overview of common problems, and describes the broader impact of inaccurate or infrequent well tests, with a focus on production testing of wells in the Permian Basin. Many of these challenges, however, apply to onshore oil and gas fields around the world. To overcome the measurement challenges in a cost-effective manner, the industry has taken multiple approaches to create various inline test devices with limited success. The authors introduce a measurement system that is agile for transport and can be installed anywhere with a small footprint while delivering reasonably accurate results.

Introduction

Measurement-system design included the following requirements:

- Able to measure oil, water, and gas flow rates with reasonable accuracy

- Agility allowing the system to be moved rapidly and easily by using a trailer behind a work truck

- Installable and operational within 6 hours

- Maximum 8×8-ft footprint

- Must run standalone or in series with any other measurement system for validation testing

- No requirement for additional infrastructure—capable of operation under its own power and communication with cellular or satellite phones and modems

Theory and Methods

Industry Practices: Importance of Accurate Well Tests. The standard test requirement for regulatory reporting in most provinces and states in North America is two 24-hour well tests per month. The 2 or more days of testing in a test separator, and the remaining days tested in a group separator, are used to estimate total monthly production volume allocated to the well. A sales meter is used to measure group production from a satellite for allocating revenues to the working-interest (WI) holders of each well or lease. In almost all fields, the production measured at the sales node does not match the combined production from multiple group lines that are run into the sales line. This poses a challenge because the sum of group lines is different from the volume measured by the sales meter. The challenge is addressed by prorating the difference between the sales meter and group lines back to the individual wells, called the proration factor.

In the event of disagreement among WI owners, a large proration factor may cause custody-transfer issues. The good news is that the industry has developed many products used in specific applications to increase testing frequency and accuracy. The proposed measurement system fits well into this application and into much broader measurement categories. The measurement system was tested at Apache with highly favorable results and is ready to be deployed to optimize production allocation, well-test accuracy, and metering accuracy.

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