Innovative Technology in Production Operations
Authors: Reis P.J. , Marko W.A. , Eiesland O.M. , Hudson C.W. , Cain W.D. , Barbieri R. , Sharpe G.F. , Breeze A.F. , Bechthold H.D. , Reagan J. , Canalizo C. , Rieth N.C. , Auzenne B.M. , Maloney T.R. , Patterson D.E. , Aseltine R.J. 
Published: December 2007

Reis, P.J.;* Getty Oil Co.; Marko, W.A.;* Mobil Oil E&P Southeast Inc., and Eiesland, O.M.;* Mobil Exploration Norway Inc.; Hudson, C.W.;* Exxon Co. U.S.A.; Cain, W.D.;* Exxon Co. U.S.A.; Barbieri, R.;* Amoco Argentina Oil Co.; Sharpe, G.F. and Breeze, A.F.;* Chevron U.S.A. Inc.; Bechthold, H.D.* and Reagan, J.; Otis Engineering Co., and Canalizo, C.; Retired; Rieth, N.C.;* Mobil Oil E&P Southeast Inc.; Auzenne, B.M.; Exxon Co. U.S.A.; and Maloney, T.R.; Patterson, D.E.;* and Patterson, D.E.;* and Aseltine, R.J.;* Chevron U.S.A. Inc.

The Production Operations Forum is designed to allow the discussion of and dissemination of information about technical innovations and solutions in production engineering that are of immediate practical production engineering that are of immediate practical use but do not warrant a full-scale paper. Each subject is presented in a five to eight minute period with a discussion period of seven to ten minutes. A wide range of subjects is encompassed in the session. Abstracts of the presentations follow.

1. "A Successful Implementation of Microprocessors as Time Cycle Control Devices in an Intermittent Gas Lift Operation"

This presentation was prepared to share with the industry a successful implementation of microprocessors as time cycle control devices for intermittent gas lift operations. In the Ventura Avenue field, Getty Oil Company operates 125 intermittent gas lift wells. The wells are all on time cycle control and used to be controlled by an electric-driven clock intermitter at each well site. However, as with any mechanical timing device, no two ran exactly alike. Some had a tendency to lose time while others gained time. This often resulted in an upset of a previously balanced system.

When too many wells receive gas, the compressor discharge pressure drops significantly, because the maximum discharge rate is being divided up to too many wells. These wells are often undergassed in this situation and usually load up. This results in lost production and increased operating costs because the wells must be kicked before they can be returned to normal intermittent lifting operations.

When very few wells receive gas due to an imbalanced system, compressor discharge pressure increases and those wells receiving gas are overgassed. Overgassing is inefficient and is reflected in high single-well gas-liquid ratios (GLR's). High pressure gas that cannot be forced into those few wells receiving gas must be released into the low pressure system. Fuel gas is wasted resulting in inefficient operations.

Inaccurate time cycle controllers can therefore be a significant problem for large intermittent gas lift operations. Their inaccuracy can cause skipped cycles which results in frequent unloading of wells. In addition, unnecessary overgassing results in wasted compressor fuel gas. Individual well GLR's are adversely affected and the overall system efficiency is lowered.

The microprocessor assisted programmable controllers have alleviated the problems caused by inaccurate intermitters. A master clock, accurate to one-tenth of a second, governs each programmable controller. Each day at 12:00 noon, the master clock encodes a radio transmitter and a tone is sounded which resynchronizes each controller. This insures that all of the controllers will never drift from the master clock.

The microprocessor assisted programmable controllers also make it much easier to optimize each well. Altering the number of cycles per day, or the duration of gas injection period, is now done from several centralized locations instead of 125 individual well sites. Prior to the installation of the programmable controllers, optimizing a well was difficult programmable controllers, optimizing a well was difficult to do because a system would never remain balanced more than a few days at a time.

The cost to purchase and install the microprocessor assisted programmable controllers and related equipment was approximately $100,000. From January, 1982 and January, 1983, the average compressor fuel usage had decreased from 55 MMCF/mo. to 40 MMCF/mo. Using an average gas price of $3.50/MCF, this decreased fuel usage has resulted in a savings of over $600,000 in one year.

Microprocessor assisted programmable controllers have played a major role in optimizing the intermittent gas lift system in the Ventura Avenue field. Conclusions based on the data obtained since the installation of the controllers are as follows:Compressor discharge rate and pressure fluctuations due to inaccurate intermitters have been eliminated resulting in more efficient gas lift operations.