Improved Circulating Temperature Correlations for Cementing
Authors: Goodman M.A. , Mitchell R.F. , Wedelich H. , Galate J.W. , Presson D.M. 
Published: December 2007

This paper describes the results of a three-year joint industry project to develop improved circulating temperature correlations for casing cementing, liner cementing, tieback cementing, and squeeze cementing. The correlations were developed from over 2,000 simulation cases with a wellbore thermal simulator and compared to field measurements. The correlations apply to offshore and deviated wells, and account for thermal disturbance of the drilling operations with both water base and oil base muds.

The temperature correlations are designed so that they can be used at several levels of accuracy depending on the circulation parameter, a new dimensionless quantity formulated in terms of key operational variables. The simplest application uses estimates of the circulation parameter based on the API data used to compile the current API standards. The next level of accuracy determines the circulation parameter under the assumption of a default set of parameter under the assumption of a default set of well conditions that represent the thermal disturbance due to drilling. The highest level of accuracy is achieved by modifying the default drilling correlation to account for the actual drilling variables.

Introduction

In 1941, the API Committee on Standardization of Oil-Well Cements established a set of circulating temperature guidelines based on measured data from five gulf coast wells. This empirical correlation was presented as a function of depth for a constant static gradient of 1.5 F/100 ft. In the early 1970's, the API upgraded the correlation with field data from approximately 80 gulf coast wells by presenting the circulating temperature as a function presenting the circulating temperature as a function of both depth and static gradient. In an API technical paper on the enhanced correlations, Art Tragesser, Chairman, and Frank Shell, member, of the API Task Group noted that well temperatures depend on many variables besides depth and gradient. Tragesser and Shell state: "Certainly, varying well conditions such as depth, mud properties, circulation rates, hole sizes, pipe sizes and thermal status can affect circulating temperatures." In 1984, Venditto and George compared the API schedules to measurements from 52 additional wells. Only 60% of the wells agreed with the API schedules within 10 F. Twenty-six percent differed by 10–20 F, and 13% differed by more than 20 F.

Drilling in different regions of the world, such as Alaska or the North Sea, presents different sets of drilling conditions. Deeper wells, highly deviated wells, and drilling with oil base systems present conditions where the API standards may not present conditions where the API standards may not apply. Measurements with downhole gages on drill pipe have shown that circulating temperatures can be pipe have shown that circulating temperatures can be off by as much as 50–100 F from the API guidelines. Results from wellbore thermal simulation demonstrate that flow rate, mud type, inlet temperature, and casing size can significantly affect bottomhole circulating temperatures. For liner tops and squeeze cementing, it has been recognized that the API charts need to be extended.

In 1983, a joint industry project was launched to develop improved cementing temperature correlations. Nine companies participated in the project, including three North Sea operators. The project, including three North Sea operators. The project was divided into three phases. Phase 1 project was divided into three phases. Phase 1 compared measured data from 10 wells supplied by participants to predicted temperatures using a participants to predicted temperatures using a wellbore thermal simulator. Phase 2 quantified the differences in circulating temperatures due to different parameters. Results confirmed that while depth and static gradient are the two most important parameters, many other variables can significantly parameters, many other variables can significantly impact circulating temperatures, particularly for deeper wells. Phase 3 developed improved circulating temperature correlations with the wellbore simulator.

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