Gas Measurement and Control System Improves
Profitability of Anadarko Petroleum Corporation

By Mark Rinehart
Anadarko Petroleum Corporation

Anadarko Petroleum Corporation is an independent oil and gas exploration and production company with operations in the Hugoton gas field located in the central region of the United States. Anadarko operates approximately 2,000 gas wells within a seven county area. Approximately 1600 wells are utilizing electronic flow measurement and the remaining wells continue to use circular chart recorders or EGM (Electronic Gas Measurement) operated by third party systems. Pressures at each well range from 5 to 30 PSIG and the typical well depth is 2800 feet.

Anadarko manages its gas fields with the help of a measurement and control system consisting of remote operations controllers (ROCs) and control valves from Fisher Controls International, Inc. Flow variables are measured with pressure and temperature transmitters from Rosemount, Inc. FIX-DMAC software from Intellution, Inc. and custom applications software coded by B.J. Alberts Co., a Fisher Representative, is the interface at the host between technicians and the ROCs. Data is transmitted via point to multipoint and point to point radios (both private frequency and spread spectrum) from Microwave Data Systems.

System Overview

A typical well site installation operates with the Fisher Type ROC312 to perform real-time flow measurement and control, data collection and storage, and the Kansas State Well Test. The ROC measures gas flow based on pressure and temperature readings from Rosemount transmitters connected across an orifice plate on a meter run. A Fisher control valve equipped with an electric actuator controls gas flow. The equipment is solar powered with battery backup and communication to the host is by radio. Future plans for sites include using the ROC to measure salt water tank level, control pumping units, and monitor compressor status.

Although the ROC can handle more than one meter run, about 70 percent of the sites use one ROC per meter run due to the distance between runs. The balance of the sites utilizes one ROC for two meter runs. Where two ROCs are located reasonably close to one another, the radio is shared.

The field is monitored and controlled by a host system at Anadarko's office which is located in the southeast corner of the field. A microwave link connects the office to a radio tower located about 65 miles away. The distance from the tower to individual wells can be up to 30 miles. The host system consists of three personal computer "nodes" networked to a Windows NT file server. A "master node" runs Intellution FIX-DMAC software and performs data collection and distribution, interim data storage, and operator interfacing functions. The PC's communicate with the ROCs by radio. A separate computer running custom software from B.J. Alberts Co. is used for gas measurement recalculation, reporting, and flow control scheduling.

Increased Production

Gas production in the Hugoton Field is regulated by the State of Kansas. The results from bi-annual flow testing set the maximum production allowed on a monthly basis. The well test involves an initial shut-in period to build up pressure in the well followed by a draw-down and a final shut-in period where the resulting pressure and flow is critical in determining the allowable production for the well.

Before the system was installed, an operator manually adjusted flow and pressure to conduct the test. Now, the test is controlled by the ROC around the clock, and test results are uploaded to the host for archiving and reporting. Anadarko estimates that allowed production is 4 to 6 percent higher with automated well testing than with manual testing.

The daily operations report and on-line well information at the host provide operations data for each well. The report is automatically sent to field personnel each morning. By using this information, they can prioritize their efforts and quickly resolve issues that could result in reduced gas flow. This is especially critical in winter when demand is high and extensive time and effort may be required to reach sites. The availability of operating data has increased overall flow and improved the flow balance for the field. Anadarko estimates an additional 2 to 3 percent production increase is attainable from reduced down time.

The system incorporates sophisticated modeling logic that balances the desired flow from each well such that the overall flow to compressors remains constant. This requires that marketing information be supplied to the host to set start time, duration of flow, and flow rate. The data is downloaded to each ROC, which can operate independently of the host for up to one month. By using this flow balancing method, compressor throughput is optimized and total flow from the field is increased.

Two other enhancements that have increased production are accurate production control and automated adjustment for pressure changes. The ROC achieves the desired production total with automated valve control. Prior to automated control, operators could shut off a well below its desired production because they might not return to the site in time to prevent excessive production. The ROC continually adjusts the valve to achieve the desired flow rate as pipeline and well pressures change.

Added Product Value

Gas production volumes are susceptible to weather (demand) and subsequently market price.

As market changes and opportunities are identified, short-term gains are achieved by increasing or decreasing production for the spot market. Using the flow control features of the system, a new field flow rate and control strategy can be implemented within minutes after being downloaded to the system from the company's marketing department located in Houston, Texas.

Also, because of the system's ability to control well production and overall field flow, a customer is assured of delivery which lets Anadarko market its gas at a premium and obtain new business.

Reduced Operating Costs

Using automated field information, field operators are responsible for about 50 percent more sites than with manual control. Without automation, an operator could only cover an average of 100 well sites, but the automation system allows coverage of 150 or more sites in an area of 30 to 60 square miles. This increase in efficiency has allowed Anadarko to add wells through drilling and acquisitions without substantially adding personnel, and reducing contract services for well monitoring by $60,000 per month. Anadarko is also able to add pumping units (which remove water from the well column that can prevent gas flow), and compressors without adding personnel.

With automation, field operators only travel to a site when a problem arises. Because only selected sites are visited, costs have been reduced for contracted services as well. For example, in winter months heavy equipment is required to travel to some well sites. By eliminating wasted trips, road damage is reduced and expenses are kept to a minimum.

Improved Data Exchange

Production information from the system is made available to various departments within the company. Production accounting captures the data to improve billing accuracy and reduce the billing cycle time by as much as two weeks. Production data is analyzed by engineering to maintain individual well performance and for gas reserve analysis. The result of these analyses improves flow rates, reduced maintenance costs and optimize cash flow.

Recent Example of System Benefits

During the first week of February 1996, the temperatures in Kansas dropped below zero for a number of days during a record-setting arctic cold system that covered most of the United States. Demand for gas production was at its highest in years, with spot market prices for gas from $10 to $12 per MCF, compared with typical prices of $2 to$3 per MCF. These same conditions can reduce production dramatically because facilities can freeze and pumping units and field compressors are difficult to keep on-line and maintained.

Anadarko's automation system operators modified the configuration of their Intellution host so that it polled the entire field and generated operation reports several times during a day. These reports were automatically sent to field personnel 24 hours a day, seven days a week. Field management used this information to identify wells that were not producing as expected and to dispatch maintenance personnel in a timely manner.

During this time, the transportation pipeline in which Anadarko delivers gas experienced a 20% reduction in scheduled deliveries. Anadarko, who delivers about one-half of the pipeline company's supply, reduced deliveries by only 5%. With an integrated automation system, Anadarko was able to deliver 95% of its planned production while their competition delivered 65% of its planned production.

In the weeks that followed the cold spell, gas distribution customers were requesting information as to why they had not received adequate gas. Anadarko quickly and easily supplied information showing that their production had met contractual requirements.

These events clearly demonstrated many of the anticipated benefits of the system. Lost revenue was minimized, added value was received for part of production, operating costs were minimized through timely information gathering, and a high level of customer satisfaction was achieved.

The system will continue to be expanded through new drilling, possible acquisitions and partnerships, and contract operating agreements.