Methods and apparatus for borehole measurement of formation stress

• US 5,517,854 A
• Filed: 04/29/1994
• Issued: 05/21/1996
• Est. Priority Date: 06/09/1992
• Status: Expired due to Term

• Current Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Original Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Inventors: Dave, Yogesh S., Plumb, Richard A.
• Primary Examiner(s): Brock, Michael J.
• Application Number:
  US08/236,356
• Time in Patent Office: 753 Days
• Field of Search: 73/151, 73/155, 73/784, 166/250, 166/101, 166/308, 166/264, 166/271
• US Class Current: 73/152.59
• CPC Class Codes: E21B 49/008 by injection test; by analysing pressure variations in an injection or production test, e.g. for estimating the skin factor measuring pressure E21B47/06
• CPC Class Codes: E21B 49/08 Obtaining fluid samples or testing fluids, in boreholes or wells

Abstract

A modular sonde may be configured in various ways for measurements in open or cased boreholes. The sonde is conveyed on an electric wireline with or without a coiled tubing for conveying hydraulic energy from the surface. Modules common to the configurations include telemetry electronics, orientation, hydraulic energy accumulator, fluid chambers, hydraulic power, pumpout, and flow control. Each configuration has a stress/rheology module suited to the borehole situation. An open-hole sonde configuration has a stress/rheology module with an instrumented, inflatable packer module, an orienting module, and a probe module. A second open-hole sonde configuration has a stress/rheology module with an instrumented straddle-packer assembly. A cased-hole sonde configuration has a gunblock assembly, a gunblock orienting module hydraulics for formation pretest and hydraulics for stressing the formation to obtain data related to formation stress characteristics. A second cased-hole sonde configuration has a straddle-packer assembly, a casing perforation device in the straddle interval, and hydraulics for stressing the formation to obtain data related to formation stress characteristics.

Claims

1. A system for obtaining measurements in a borehole from which in-situ stress of an underground formation can be estimated, wherein the system comprises a sonde and an electric wireline cable connected to the sonde for conveying the sonde in the borehole, and wherein the sonde comprises:

a) pressure-creating means producing hydraulic energy;

b) a stress/rheology module coupled to the pressure-creating means via a flow line and having an inflatable packer and a controllable valve coupled to the inflatable packer and to the flowline for establishing hydraulic communication between the inflatable packer and the flowline for receiving hydraulic energy therefrom and applying to the formation at a controlled rate a force opposing in-situ stress in the formation, pressure sensing means for monitoring a pressure related to the force applied to the formation by the inflatable packer, means for monitoring inflation fluid flow to the inflatable packer to determine inflation volume of the inflatable packer, and an acoustic sensor for detecting acoustic emissions in the borehole as the force is applied to the formation;

c) force reducing means coupled to the inflatable packer for controllably reducing the force applied to the formation; and

d) a flow control means in hydraulic communication with the borehole for withdrawing formation fluid from the formation at a controlled rate for pressure draw-down pre-test and comprising a probe affixed to and movable relative to the sonde, an orienting module mechanically coupled to the probe for controllably positioning the probe at a selected rotational position around a longitudinal axis of the sonde, a controllable actuator mechanically coupled to the sonde and to the probe for applying the probe to the borehole wall, and a flow control module hydraulically coupled to the probe at constant pressure.

2. A system as claimed in claim 1, further comprising a hydraulic energy source located outside the borehole, and a tubing for conveying hydraulic energy from the source to the sonde for charging the stress/rheology module with hydraulic energy while the sonde is in the borehole.

3. A system as claimed in claim 1, wherein the force reducing means comprises a controllable flow-back valve coupled to the inflatable packer for releasing hydraulic energy therefrom at a controlled rate when the flow-back valve is opened.

4. A system as claimed in claim 1, wherein the force reducing means comprises a pump-out module, the pump-out module comprising a controllable pump assembly in hydraulic communication with the inflatable packer for pressurizing and depressurizing the packer.

5. A system as claimed in claim 1, wherein the stress/rheology module further comprises a plurality of displacement sensors attached to the sonde and disposed for detecting radial displacement of the borehole walls at multiple locations about a central axis of the sonde.

6. A system as claimed in claim 5, wherein the sonde further comprises an orientation module forming an integral part of the sonde and having sensors for detecting orientation of the sonde in the borehole relative to the earth'"'"'s gravitational field and relative to the earth'"'"'s magnetic field.

7. A system for obtaining measurements in a borehole from which in situ stress of an underground formation can be estimated, wherein the system comprises a sonde and an electric wireline cable connected to the sonde for conveying the sonde in the borehole, and wherein the sonde comprises:

a) an accumulator module having a reservoir for storing hydraulic fluid, a flow line, and a controllable valve coupled to the reservoir and to the flow line for controlling transfer of hydraulic fluid between the reservoir and the flow line;

b) a stress/rheology module coupled to the accumulator module and having force applying means coupled to the flow line for receiving hydraulic fluid from the flow line and applying to the formation at a controlled rate a force opposing in-situ stress in the formation wherein the force applying means comprises an inflatable packer and a controllable valve coupled to the inflatable packer and to the flowline for establishing hydraulic communication between the inflatable packer and the flowline, means for monitoring inflation fluid flow to the inflatable packer to determine inflation volume of the inflatable packer, and an acoustic sensor for detecting acoustic emissions in the borehole as the force is applied to the formation;

c) force reducing means coupled to the force applying means for controllably reducing the force applied to the formation; and

d) a flow control means in hydraulic communication with the borehole for withdrawing formation fluid from the formation at a controlled rate for pressure draw-down pre-test, the flow control means comprising a probe affixed to and movable relative to the sonde, an orienting module mechanically coupled to the probe for controllably positioning the probe at a selected rotational position around a longitudinal axis of the sonde, a controllable actuator mechanically coupled to the sonde and to the probe for applying the probe to the borehole wall, and a flow control module hydraulically coupled to the probe to drawing fluid through the probe at constant pressure.

8. A system as claimed in claim 7, wherein the stress/rheology module further comprises a plurality of displacement sensors attached to the sonde and disposed for detecting radial displacement of the borehole walls at multiple locations about a central axis of the sonde.

9. A system as claimed in claim 8, wherein the sonde further comprises an orientation module forming an integral part of the sonde and having sensors for detecting orientation of the sonde in the borehole relative to the earth'"'"'s gravitational field and relative to the earth'"'"'s magnetic field.

10. A system as claimed in claim 7, further comprising a hydraulic fluid source located outside the borehole, and a tubing for conveying hydraulic fluid from the source to the sonde for charging the stress/rheology module with hydraulic fluid while the sonde is in the borehole.

11. A system as claimed in claim 7, wherein the force reducing means comprises a controllable flow-back valve coupled to the inflatable packer for releasing hydraulic energy therefrom at a controlled rate when the flow-back valve is opened.