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Abstract

This paper presents the results of the implementation of compression to increase the deliverability of Clinton sandstone natural gas wells by lowering the effective line pressure against which the wells must produce. Graphs in this paper display the historical producing rates with time, both before the compression was implemented and after the compression was implemented. The wells studied are producing natural gas through the tubing, through valves that open and close intermittently with duration of flow time and shut-in time controlled by clocks. Some of the wells have controls located at the wellhead and some are controlled at the separator. Comparisons are made between estimated reserves that would have been produced and accompanying economics without compression versus estimated reserves to be produced and accompanying economics with compression. The estimated incremental reserves and revenue are compared to the initial cost to install the compression. Duration of intermittent flow times and shut-in times and the accompanying pressures before compression are compared to those subsequent to implementation of compression. Comments are included concerning the use of the "decline curve" to estimate natural gas reserves.

Introduction

The use of natural gas compressors to deliver gas from low pressure wells into higher pressure gas gathering systems has pressure wells into higher pressure gas gathering systems has obvious benefits. However, when considering the use of compression to increase deliverability and reserves from Clinton sandstone producing wells in the state of Ohio, the results and benefits are more difficult to predict. Annual flow tests, semi-annual shut-in pressures, and initial back-pressure tests are not required by the agency that regulates the production of natural gas in Ohio. Therefore, the collection of empirical data concerning actual case histories should be beneficial in the estimation of results to be expected from the implementation of compression involving future projects.

Case histories and comments

Figures 1 through 5 exhibit a portion of the history of each well's or group of wells' producing rates in thousand cubic feet of gas, MCF (28.317 m3) per month prior to compression, versus after compression. Natural gas reserves and economics were estimated, as of the date that compression was installed for two (2) cases for each well or group of wells:

  1. without compression;

  2. with compression.

These estimations are displayed in Table 1 and Table 2. Each table includes estimated gross (100%) reserves, estimated net reserves, estimated future net revenue (after subtracting all operating costs, severance and ad valorem taxes) and present worth of estimated future net revenue discounted at 20 percent. Estimated future net revenue ignores initial compressor installation in Tables 1 and 2.Table 3 displays estimated incremental gross and net reserves attributable to the wells' increased natural gas production resulting from compression effects, estimated incremental discounted future net revenue attributable to the estimated incremental net reserves, and initial costs to install compression.

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