Using Drilling and Completions Temperature Measurements To Estimate Formation Temperatures In A Research Test Well

This paper strives to estimate annulus fluid and casing temperature profiles using published models and the temperature measurements during drilling and completions operations. With known wellbore radius, fluid temperature at the end of circulations, circulation duration and formation thermal diffusivity, either a pseudo temperature log or the undisturbed static formation temperature (SFT) can be calculated if either a temperature log or the SFT profile is known. Typically, in an active oil and gas or geothermal drilling region, an SFT trend versus true vertical depths (TVD) becomes available from a regional geological or geophysical study. Likewise, the unknown formation SFT can also be estimated using an available temperature log measured at a specified time. In a research test well located in Grimes County, Texas, both the SFT and multiple temperature logs are obtained during open-hole drilling and completions phases. In this paper, the SFT is assumed known and used to estimate the various temperature logs that were acquired during drilling and completions operations through memory MWD (measurement-while-drilling) tools, live-streaming EMS (enhanced measurement sub) / ASM (along-string measurement) tools in the open-hole and fiber-optic measurements in the case-hole. Encouraging recovery temperature predictions are obtained along the full range of wellbore depths that satisfactorily match the actual downhole temperature measurements. In this study, one critical input data, the formation thermal diffusivity, is selected from published literatures and calibrated by modeling and calibrating the temperature recovery for a given depth. To compute a pseudo temperature log, a dimensionless temperature recovery solution is first produced with the knowledge of dimensionless circulation time, dimensionless recovery time, wellbore dimension and thermal diffusivity. Then a dimensional analysis can solve the wellbore recovery temperature at a given time with a known SFT trend or vice-versa. In the open-hole case, the fluid circulation time is practically adjusted to reflect the ‘true’ circulation time to start from the moment that the drill bit contacts the formation at a specific depth in order to honor the initial formation temperature condition at the beginning of the fluid circulation. Therefore, only at the total depth of the well, the ‘true’ circulation time for the heat emission from the wellbore is the actual circulation bottom-up (CBU) time but at other depths it varies with depths and is much greater than the CBU time. In the cased-hole case, the published analytical solutions can be applied directly for all depths as the initial conditions are honored when the circulation begins after an extended shut-in time elapsed. The case studies demonstrated in the test well illustrate that the temperature logs or the SFT can be predicted very accurately with the published analytical solutions when the correct initial temperature conditions apply.

REFERENCES Carslaw, H.S., and Jaeger, J.C.: Conduction of Heat in Solids, 2nd Ed., Oxford Univ. Press, London, (1959). Jaeger, J.C.: Numerical Values for the Temperature in Radial Heat Flow, Jour. of Math. Phys., 34 (1956), 316-321. Kutasov, I.M.: Dimensionless Temperature, Cumulative Heat Flow and Heat Flow Rate for a Well With a Constant Bore-face Temperature, Geothermics, 16, No. 2, (1987), 467-472. Kutasov, I.M., Caruthers, R.M., Targhi A.K., and Chaaban, H.M.: Prediction of Downhole Circulating and Shut-in Temperatures. Geothermics, 17, (1988), 607-618.