Using Downhole Annular Pressure Measurements to Anticipate Drilling Problems

Abstract

Downhole annular pressure is becoming a standard measurement in all drilling environments. When monitored in the context of other drilling parameters, and with a fundamental understanding of hydraulics principles it is possible to identify undesirable drilling conditions, suggest remedial procedures, and help prevent serious problems from developing. For wells with only a small difference between fracture gradient and pore pressure, drilling without realtime downhole annular pressure information may not be possible. Indeed, this is particularly true for extended reach wells, for high temperature / high pressure (HTHP) wells, and in deep water environments where large flowing friction pressure losses or very narrow pressure margins can exist. Previous publications have discussed how with realtime downhole annular pressure measurements a driller can more effectively maintain the equivalent circulating density (ECD) and equivalent static density (ESD- when not circulating) within a desired range in order to prevent lost circulation and maintain borehole integrity (including managing swab, surge and gel breakdown effects). Annular pressure data are used to evaluate the effects of flow and pipe rotation on the ECD, and to evaluate formation integrity tests. With accurate downhole data the driller can apply conventional drilling practices more effectively to reduce both rig time and potentially also the number of required casing strings. In order to interpret annular pressure measurements it is important to first understand the physical hydrodynamic principles. It is also important to analyze pressure data in the context of all downhole and surface drilling parameters. Recent experiences with downhole pressure data have demonstrated how ECD trends can be used to anticipate drilling problems before they develop into serious events. Even with the ECD within its desired range, drilling problems not apparent from conventional procedures can be anticipated. We present three case histories. The first is from an extended reach drilling project where the annular pressure data gave advanced warning of high cuttings loading, and helped avoid a potential lost circulation or stuck pipe event. This example also illustrates the significant flowing pressure losses that can occur along an extended reach wellbore. A second case history demonstrates the importance of using annular pressure measurements in deep water environments both to establish and maintain safe pressure margins. Downhole pressure data can also be used to evaluate kill procedures. The final example was from an extended reach well where the drilling fluid had sagged during a bit trip, and shows how by evaluating downhole annular pressure measurements, safer and more efficient tripping practices can be developed. P. 535

Annular Frictional Pressure Losses During Drilling—Predicting the Effect of Drillstring Rotation

“…Fiveteen years later Hemphill et al [27] reported similar results for a North Sea well. Field data also showing a reduction in annular frictional pressure losses with increased drill string rotation does also exist [31] showing the complexity of the flow problem. …”

Effective Hydraulic Modeling and Field Data for Deepwater Horizontal Well with Low Drilling Margins in an Unconsolidated Formation

“…Hydraulic software has been proven to provide effective ECD prediction (van Oort et al 2004;Guarneri et al 2005;Hutchinson and Rezmer-Cooper 1998;Mallary and Varco 1999;Peters et al 1988;Roy and Zamora 1005;White et al 1997;Zamora 1997;Zamora and Roy 2000;Zamora and Roy 2001;Zamora et al 2006). Thus modeling was utilized to predict the ECD as well as hole cleaning at densities of 9.15 to 9.2 lb/gal for the RDF system.…”

The Use of Resistivity-at-the-Bit Images and Annular Pressure While Drilling in Preventing Drilling Problems

“…However, the annular pressure measurement or ECD can only yield so much information on its own. The pressure data should be displayed in the context of the other drilling variables for useful diagnosis of drilling problems [3].…”

“…In addition, a few intervals show a much larger feature, but over a shorter 60 ft interval. To best interpret this data, all LWD measurements should be integrated [3].…”