Challenges With Jointed-Pipe Underbalanced Operations

Abstract

Successful underbalanced operations demand a systematic approach with integration of engineering, operations, production, reservoir, and geology. There are significant advantages to underbalanced drilling (UD). Formation damage can be minimized if proper circulating fluids and operating parameters are chosen; there is an opportunity for reservoir evaluation and characterization while drilling; lost circulation and differential sticking can be avoided, combined with improvements in drilling rate of penetration (ROP); and it also provides an alternative method of well control.This paper discusses engineering challenges and considerations for underbalanced operations using multiphase flow as well as advances made during UD with rotary jointed pipe. Excluding air, mist, and foam, underbalanced techniques with multiphase fluids are reviewed. Much of the discussion and concepts also apply to coiled-tubing underbalanced operations.

Aerated Underbalance Drilling Screening Assessment at “X” Geothermal Field

“…And alternatif one only gives a limit of underbalance diferential from pore pressure @ 5 years for around 30-50 psi. This is not an ideal condition since a bottom hole pressure fluctuation on drilling connections (Saponja, 1998) needs a minimum safety factor for connection condition for about 350 psi. If this alternatif is applied then when pipe connection, it will absolutely become overbalance.…”

“…Considering the bottom hole pressure fluctuation on drilling connections (Saponja, 1998) addtional factor, then a range of Qliquid at 0.10ft 3 /s and a range of Qgas around 2.90 ft 3 /s -3.20 ft 3 /s should be implemented.…”

Uncertainty Assessment in Well Productivity Loss due to Formation Damage

“…However, in an underbalanced operation, it is difficult to guarantee that the drilling fluid pressure is always in underbalanced condition 11 . An overbalanced pressure can still be applied on the formation during certain period for various operational reasons like bit trips or well intervention and it can cause a severe formation damage due to the absence of filter cake protection and huge filtrate invasion.…”

“…To better evaluate formation damage due to drilling fluid, significant efforts have been made in order to develop laboratory techniques [1][2][3][4][5][6][7][8][9][10][11][12] . Formation damage tests allow to evaluate return permeability after a core sample has been subjected to the tangential flow of a drilling fluid.…”

“…In overbalanced drilling (OBD), formation damage is caused by the presence of filter cakes and invading drilling fluid in porous media [1][2][3][4][5][6][7][8][9] . In underbalanced drilling (UBD), even if the pressure gradient is negative, drilling fluid invasion into reservoir can still occur due to the presence of capillary pressure or temporary overbalanced pressure [10][11][12] . The economic impact of poor productivity of open hole wells has pushed toward significant efforts in recent years to study laboratory testing techniques 10,11 and numerical modelling methods [13][14][15][16][17][18][19][20][21] for assessing drilling induced formation damage.…”