Changes

The same information is available from long-term production tests as from short-term flow tests, including permeability, skin factor, and distance to boundaries. Hydrocarbons in place in the tested well's drainage area can frequently be estimated from these test data. Once boundaries have affected the test data, long-term production data can be extrapolated to provide a forecast of future production to the economic limit and can thus provide a reserve estimate for the well.

The same information is available from long-term production tests as from short-term flow tests, including permeability, skin factor, and distance to boundaries. Hydrocarbons in place in the tested well's drainage area can frequently be estimated from these test data. Once boundaries have affected the test data, long-term production data can be extrapolated to provide a forecast of future production to the economic limit and can thus provide a reserve estimate for the well.

===How the tests are run===

===How the tests are run===

These “tests” are applicable at any time. The data are most readily analyzable if the well is produced at approximately constant BHP or when BHP and flow rate are known continuously as functions of time.

These “tests” are applicable at any time. The data are most readily analyzable if the well is produced at approximately constant BHP or when BHP and flow rate are known continuously as functions of time.

===How the tests are analyzed===

===How the tests are analyzed===

[[file:pressure-transient-testing_fig8.png|thumb|{{figure number|8}}History match of production data and forecast of future performance.]]

 

[[file:pressure-transient-testing_fig6.png|thumb|{{figure number|6}}Fetkovich's type curve for analyzing long-term production data. (After <ref name=pt09r8>Fetkovich, M. J., 1980, Decline curve analysis using type curves: Journal of Petroleum Technology, June, p. 1065–1077.</ref>.)]]

 

An essential requirement in this method of analysis is that there is enough production history for boundary effects to have influenced production data. This same requirement also applies to conventional decline curves and decline curve analysis—if boundary effects have not been felt, the decline curve projection is totally meaningless and certainly incorrect. Figure 7 shows a type curve match of past performance and indicates how production data can be extrapolated into the future.

[[file:pressure-transient-testing_fig7.png|thumb|{{figure number|7}}Actual production data matched on a Fetkovich type curve.]]

The simplest of these tests—those with production data from wells produced at constant BHP or with smoothly changing rates and BHP—can be analyzed with simple type curves, such as Fetkovich's, illustrated in [[:file:pressure-transient-testing_fig6.png|Figure 6]]. Formation properties are obtained from matches of actual field data to the type curve. Forecasts are made by projecting future performance along the type curve that matches post-production performance.

More complex tests, with abrupt changes in rate and BHP, are more readily analyzed with computer reservoir simulators. These simulators are used to history-match production data to obtain a reservoir description, which is then used to obtain a long-term production forecast and thus to estimate reserves. Figure 8 shows an example of a history match of production data and a forecast of future performance of the well using the reservoir description obtained from the history match.

An essential requirement in this method of analysis is that there is enough production history for boundary effects to have influenced production data. This same requirement also applies to conventional decline curves and decline curve analysis—if boundary effects have not been felt, the decline curve projection is totally meaningless and certainly incorrect. [[:file:pressure-transient-testing_fig7.png|Figure 7]] shows a type curve match of past performance and indicates how production data can be extrapolated into the future.

[[file:pressure-transient-testing_fig8.png|thumb|{{figure number|8}}History match of production data and forecast of future performance.]]

More complex tests, with abrupt changes in rate and BHP, are more readily analyzed with computer reservoir simulators. These simulators are used to history-match production data to obtain a reservoir description, which is then used to obtain a long-term production forecast and thus to estimate reserves. [[:file:pressure-transient-testing_fig8.png|Figure 8]] shows an example of a history match of production data and a forecast of future performance of the well using the reservoir description obtained from the history match.

==Interference and pulse tests==

==Interference and pulse tests==