Drilling normally to sub-normally pressured formations
A system and method for drilling a substantially horizontal well bore in a normally to sub-normally pressured formation. The normally to sub-normally pressured formation is an unconventional reservoir. The well bore is drilled over-balanced with a drilling fluid including a fluid loss agent. The fluid loss agent is operable to form a filter cake on the well bore during drilling.
1 . A method for drilling a well bore, comprising:
drilling a substantially horizontal well bore in a coal seam; and
drilling the well bore over-balanced with a drilling fluid comprising at least one of aphrons and micelles to form a filter cake on a wall of the well bore during drilling.
2 . The method of claim 1 , wherein the drilling fluid comprises a density at or greater than 9.5 pounds per gallon.
3 . The method of claim 1 , wherein the drilling fluid comprises a density at or greater than 10 pounds per gallon.
4 . The method of claim 1 , wherein the drilling fluid comprises a density substantially the same as that of the coal seam cuttings produced by drilling the well bore.
5 . The method of claim 1 , wherein the drilling fluid comprises a viscosity agent.
6 . The method of claim 1 , wherein the filter cake invasion into the formation comprises a depth of less than 5 centimeters.
7 . The method of claim 1 , wherein the coal seam comprises at least one of naturally occurring fractures and cleats.
8 . The method of claim 1 , wherein the drilling fluid further comprises starch.
9 . The method of claim 1 , further comprising adjusting at least one of a flow rate and a property of the drilling fluid based at least in part on a difference between an actual amount of debris recovered per unit time and an expected amount of cuttings recovery per unit time.
10 . A system for drilling a well bore, comprising:
a drill bit coupled by a drill string to a rig at a surface, the drill bit operable to drill a well bore in a coal seam; and
a drilling fluid pumped through the drill string to the drill bit, the drilling fluid comprising at least one of aphrons and micelles to form a filter cake on the wall of the well bore during drilling.
11 . The system of claim 10 , wherein the drilling fluid comprises a density at or greater than 9.5 pounds per gallon.
12 . The system of claim 10 , wherein the drilling fluid comprises a density at or greater than 10 pounds per gallon.
13 . The system of claim 10 , wherein the drilling fluid comprises a density substantially the same as that of the coal seam cuttings produced by drilling the well bore.
14 . The system of claim 10 , wherein the drilling fluid comprises a viscosity agent.
15 . The system of claim 10 , wherein the filter cake invasion into the formation comprises a depth of less than 5 centimeters.
16 . The system of claim 10 , wherein the coal seam comprises at least one of naturally occurring fractures and cleats.
17 . The system of claim 10 , wherein the drilling fluid further comprises starch.
18 . The system of claim 10 , wherein the drilling fluid comprises FLC 2000.
19 . The method of claim 1 , wherein the drilling fluid comprises FLC 2000.