Field hydraulic tests improve HPHT drilling safety and performance

For the Elgin-Franklin UKCS fields, drilling of the high pressure/ high tem perature (HPHT) phase is critical due to the narrow margin between formatio n pore and fracturation pressures. This problem is accentuated by the extre me temperature (up to 205 degrees C-400 degrees F) and pressure (up to 1,20 0 bar-17,400 psi). A new generation of down-hole pressure while drilling (P WD) tools allows a better real-time monitoring of the bottom-hole pressure, but cannot withstand the extreme temperature of the entire HPHT phase. Fur thermore, down-hole and surface pressures are dependent on complex hydrauli c phenomena which make predictions challenging Consequently, it was decided to perform hydraulic tests before drilling the HPHT section of the well 22 /30c-G4 (first Elgin development well), in order to quantify the surface an d down-hole pressures and temperatures on several operating conditions: cir culating (with and without pipe rotation), tripping and how check. Gelation tests, trapped pressure as well as pressure transmission tests were also p erformed. Objectives of these tests were to better understand some complex down-hole physical phenomena, to prepare practical guidelines, before drill ing HPHT sections, to check reliability and accuracy of new real-time PWD t ools, and to collect accurate well data for further hydraulic software pack ages validation or improvement. These procedures led to great benefits, bot h in terms of safety and performance, when drilling the HPHT phases of the well: results were considered as highly positive. This paper details down-h ole measurement procedures and results, operational guide lines, tools perf ormances, lessons learnt, and explains how to cope with sources of possible discrepancies between actual values and software predictions.