Welltest 105: Thermal Data Diagnostics

Finally, Welltest Specialists believes #welltest analysis (#PTA) software should be upgraded to utilize the available temperature data for calculation of pseudo-pressure and pseudo-time variables. This should not pose a significant problem to programming code. Since thermal data are already there (essentially free for the taking), they might as well be used to better our interpretative insight and quantitative results: PTTA – Pressure-Temperature Transient Analysis… Contents of this blog were derived from the technical paper CIM...

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Welltest 105: Thermal Data Diagnostics

Welltest 105: Thermal Data Diagnostics

N2 p/T inversion curves Wet #gas (#LNG) temperature sensors (as in production logging) could easily be added to modern electronic pressure recorder designs. As the use of temperature data increases for welltest diagnostics, limitations of using recorder housing temperatures will quickly become apparent. As recorder carrier (housing) designs differ between manufacturers, so does heat capacity and thermal conductivity and, hence, apparent thermal behaviour, such as JT effects. The phenomena is illustrated by these N2 p/T inversion curves....

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Welltest 105: Thermal Data Diagnostics

Welltest 105: Thermal Data Diagnostics

Thermal Storage – Pressure Derivative Thermal Data Helpful for Identifying Valid Radial Flow Conditions. Temperature data recorded during a #welltest can be reflective of wellbore storage or afterflow effects and can help identify valid radial flow conditions. This #gas (#LNG) well #PTA example is the pressure derivative response for the thermal storage example presented last week. Note what appears to be very early radial flow followed by a transmissivity (kh/µ) change only one hour after shut-in. Thermal diagnostics suggests that...

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Welltest 105: Thermal Data Diagnostics

Welltest 105: Thermal Data Diagnostics

Complex Derivative Behaviour = Heterogeneous System Thermal Interference Demonstrated Beyond 50 m Radius. Such extensive alteration of reservoir temperatures suggests that a considerably long time might be required for the formation to return to insitu thermal equilibrium. Temperature recoveries lasting in excess of 1000 h been observed from the data provided by electronic pressure gauges. Moreover, such non-isothermal conditions might have implications on quantitative #PTA modeling results such as skin, permeability, and transient #gas...

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Welltest 105: Thermal Data Diagnostics

Welltest 105: Thermal Data Diagnostics

Joule-Thompson (JT) Cooling – Observation Well Thermal Interference Demonstrated Beyond 50 m Radius. A common assumption is that temperature changes around a wellbore do not penetrate deep into the formation during a #welltest. Considering only thermal diffusivity and conductivity of the system (steel pipe, cement, reservoir rock), this assumption is reasonable. However, Joule-Thompson (JT) cooling, a #gas expansion phenomena (#LNG), occurs at the pore throat, wherever that may be in the reservoir. The magnitude of the pressure...

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