Changes

* hydrodynamic information

* hydrodynamic information

This article focuses on ''nonflowing DSTs'' (NFDSTs). In a NFDST, fluid does not flow to the surface and a stabilized flow rate is not obtained (also, the well can flow to the surface but die or be shut-in before steady-state rates are achieved). Analysis of flowing DSTs is less complicated because flow rates can be measured throughout the test.<ref name=pt03r14>Earlougher, R. C., 1977, Advances in well test analysis: SPE Monograph Vol. 5, Society of Petroleum Engineers, New York, p. 90–103.</ref><ref name=pt03r15>Erdle, J. C., 1984, Current drillstem testing practices—design, conduct, and interpretation: Society of Petroleum Engineers Paper No. 13182, p 1–20.</ref><ref name=pt03r34>Matthews, C. S., Russell, D. G., 1967, Pressure buildup and flow tests in Wells: SPE Monograph Vol. 1, Society of Petroleum Engineers, New York, p. 84–91.</ref>

This article focuses on ''nonflowing DSTs'' (NFDSTs). In a NFDST, fluid does not flow to the surface and a stabilized flow rate is not obtained (also, the well can flow to the surface but die or be shut-in before steady-state rates are achieved). Analysis of flowing DSTs is less complicated because flow rates can be measured throughout the test.<ref name=pt03r14>Earlougher, R. C., 1977, Advances in well test analysis: SPE Monograph Vol. 5, Society of Petroleum Engineers, New York, p. 90–103.</ref><ref name=pt03r15>Erdle, J. C., 1984, Current drillstem testing practices—design, conduct, and interpretation: Society of Petroleum Engineers Paper No. 13182, p 1–20.</ref><ref name=pt03r34>Matthews, C. S., and D. G. Russell, 1967, Pressure buildup and flow tests in Wells: SPE Monograph Vol. 1, Society of Petroleum Engineers, New York, p. 84–91.</ref>

==Planning==

==Planning==

[[file:drill-stem-testing_fig1.png|200px|thumb|{{figure number|1}}Drill stem test tool string.]]

[[file:drill-stem-testing_fig1.png|200px|thumb|{{figure number|1}}Drill stem test tool string.]]

The key to successful testing depends upon planning and teamwork between the geoscientist and the engineer. Potential pay zones should be identified before drilling commences so that the drilling program can be designed to accommodate the test. If offset data are available, the magnitude of [[porosity]], permeability, and reservoir pressure should be identified. Knowledge of zonal mineralogy may prevent excessive damage by [[drilling fluid]]s and should be used in designing the mud program. The anticipated reservoir properties are used to design the test string and test times so that the best, most useable data can be obtained.

The key to successful testing depends upon planning and teamwork between the geoscientist and the engineer. Potential pay zones should be identified before drilling commences so that the drilling program can be designed to accommodate the test. If [[offset]] data are available, the magnitude of [[porosity]], permeability, and reservoir pressure should be identified. Knowledge of zonal mineralogy may prevent excessive damage by [[drilling fluid]]s and should be used in designing the mud program. The anticipated reservoir properties are used to design the test string and test times so that the best, most useable data can be obtained.

===Safety===

===Safety===

===Fluid recovery (Nonflowing Test)===

===Fluid recovery (Nonflowing Test)===

On an NFDST, the volume of fluid produced from the formation is contained in the drill string. A fluid level must be determined to calculate the volume recovered. If the fluid is highly gas-cut, a straight volume calculation will be inaccurate. Therefore, samples should be collected at regular intervals while reversing to a clean tank on location. Although it is common to reverse to a pit, the amount of fluid recovered cannot be determined if this is done. Error in measuring fluid recovery often makes the difference between an economic disaster or a success. Also, grindouts (centrifuge) must be performed on each sample to determine the percentage of oil, water, and solids. Resistivity, chloride content, and nitrate content of produced water and the specific gravity of all phases should be measured.

On an NFDST, the volume of fluid produced from the formation is contained in the drill string. A fluid level must be determined to calculate the volume recovered. If the fluid is highly gas-cut, a straight volume calculation will be inaccurate. Therefore, samples should be collected at regular intervals while reversing to a clean tank on location. Although it is common to reverse to a pit, the amount of fluid recovered cannot be determined if this is done. Error in measuring fluid recovery often makes the difference between an economic disaster or a success. Also, grindouts (centrifuge) must be performed on each sample to determine the percentage of oil, water, and solids. Resistivity, chloride content, and nitrate content of produced water and the specific [[gravity]] of all phases should be measured.

===Estimating flow rates (Nonflowing Test)===

===Estimating flow rates (Nonflowing Test)===

|-

|-

| μ

| μ

| Fluid viscosity

| Fluid [[viscosity]]

| cp

| cp

|-

|-

| Duperow

| Duperow

|-

|-

| Test Results || Pipe was pulled to the fluid in the drill pipe. The DST report indicated a recovery of [[depth::1575 ft]] of highly oil and gas-cut water at a 60% oil-cut (11.5 bbl oil and 7.7 bbl water according to pipe measurements). Total flow time on the test was 1 hour. The well was completed, fractured, and plugged after testing less than 30 BFPD. This well should have been plugged after the DST. Pressure data from the gauge above the closing tool indicated that during the flow periods, the fluid pressure in the drill string increased by 115 psig. An oil gravity of 42° API was recorded from the sample chamber. A gradient of 0.389 psi/ft was calculated for the fluid mixture in the drill pipe. A fluid column of [[length::295 ft]] of un-gas-cut fluid was recovered in the drill string. This translated into an actual recovery of 1.8 bbl of fluid (1.08 bbl oil and 0.72 bbl water).

| Test Results || Pipe was pulled to the fluid in the drill pipe. The DST report indicated a recovery of [[depth::1575 ft]] of highly oil and gas-cut water at a 60% oil-cut (11.5 bbl oil and 7.7 bbl water according to pipe measurements). Total flow time on the test was 1 hour. The well was completed, fractured, and plugged after testing less than 30 BFPD. This well should have been plugged after the DST. Pressure data from the gauge above the closing tool indicated that during the flow periods, the fluid pressure in the drill string increased by 115 psig. An oil gravity of 42° [[API gravity|API]] was recorded from the sample chamber. A gradient of 0.389 psi/ft was calculated for the fluid mixture in the drill pipe. A fluid column of [[length::295 ft]] of un-gas-cut fluid was recovered in the drill string. This translated into an actual recovery of 1.8 bbl of fluid (1.08 bbl oil and 0.72 bbl water).

|}

|}

[[Category:Wellsite methods]]

[[Category:Wellsite methods]]