Methods for evaluating inflow and outflow in a subterraean wellbore
First Claim
1. A method for identifying an inflow event in a subterranean wellbore while drilling, the method comprising:
- (a) rotating a drill bit in a wellbore penetrating a subterranean formation, the drill bit being deployed in a drill string including a plurality of axially spaced along string pressure sensors, said rotating operative to drill the wellbore and enable the inflow event in which formation fluids flow into the wellbore when the formation has a higher pore pressure than a drilling fluid pressure at a depth in the wellbore;
(b) using the plurality of axially spaced along string pressure sensors to make a corresponding plurality of axially spaced annular pressure measurements while drilling in (a);
(c) processing the plurality of axially spaced annular pressure measurements to compute a plurality of corresponding measured annular interval circulating densities and measured annular interval static densities;
(d) monitoring the computed measured annular interval circulating densities and the measured annular interval static densities while drilling in (a);
(e) evaluating a decrease in at least one of the measured annular interval circulating densities and the measured annular interval static densities and an increase in a differential flow rate as an indicator of the inflow event; and
(f) processing at least one of the measured annular interval static densities and the differential flow rate to compute a density of an inflow constituent.
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Abstract
A method for evaluating inflow or outflow in a subterranean wellbore includes acquiring first and second axially spaced pressure measurements in the wellbore. The pressure measurements may then be processed to obtain an interval density of drilling fluid between the measurement locations. A tool string including a large number of axially spaced pressure sensors (e.g., four or more or even six or more) electronically coupled with a surface processor via wired drill pipe may be used to obtain a plurality of interval densities corresponding to various wellbore intervals. The interval density may be measured during static conditions or while drilling and may be further processed to compute a density of an inflow constituent in the annulus. Changes in the computed interval density with time may be used as an indicator of either an inflow event or an outflow event.
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Citations
13 Claims
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1. A method for identifying an inflow event in a subterranean wellbore while drilling, the method comprising:
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(a) rotating a drill bit in a wellbore penetrating a subterranean formation, the drill bit being deployed in a drill string including a plurality of axially spaced along string pressure sensors, said rotating operative to drill the wellbore and enable the inflow event in which formation fluids flow into the wellbore when the formation has a higher pore pressure than a drilling fluid pressure at a depth in the wellbore; (b) using the plurality of axially spaced along string pressure sensors to make a corresponding plurality of axially spaced annular pressure measurements while drilling in (a); (c) processing the plurality of axially spaced annular pressure measurements to compute a plurality of corresponding measured annular interval circulating densities and measured annular interval static densities; (d) monitoring the computed measured annular interval circulating densities and the measured annular interval static densities while drilling in (a); (e) evaluating a decrease in at least one of the measured annular interval circulating densities and the measured annular interval static densities and an increase in a differential flow rate as an indicator of the inflow event; and (f) processing at least one of the measured annular interval static densities and the differential flow rate to compute a density of an inflow constituent. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method for identifying an outflow event in a subterranean wellbore while drilling, the method comprising:
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(a) rotating a drill bit in a wellbore penetrating a subterranean formation, the drill bit being deployed in a drill string including a plurality of axially spaced along string pressure sensors, said rotating operative to drill the wellbore and enable the outflow event in which annular fluids flow into the formation when the formation has a lower pore pressure than a drilling fluid pressure at a depth in the wellbore; (b) using the plurality of axially spaced along string pressure sensors to make a corresponding plurality of axially spaced annular pressure measurements while drilling in (a); (c) processing the plurality of axially spaced annular pressure measurements to compute a plurality of annular interval densities; (d) monitoring the computed annular interval densities with time while drilling in (a); and (e) evaluating a decrease in at least one of the annular interval densities and a decrease in a differential flow rate as an indicator of the outflow event. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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Specification