MEASURING PROPERTIES OF LOW PERMEABILITY FORMATIONS

• US 20100058854A1
• Filed: 09/10/2008
• Published: 03/11/2010
• Est. Priority Date: 09/10/2008
• Status: Active Grant

• Current Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Original Assignee: Schlumberger Technology Corporation (Schlumberger NV)
• Inventors: Waters, George, Boratko, Edward C., Latifzai, Ahmad
• Granted Patent: US 9,045,969 B2
• Time in Patent Office: Days
• US Class Current: 73/152.410
• CPC Class Codes: E21B 43/26 by forming crevices or fractures
• 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

Abstract

A method for calculating transmissibility, pore pressure, permeability and/or other properties of a subsurface layer comprising the modeling of the borehole pressure recorded from the time the subsurface layer is fractured by isolating said subsurface layer with a downhole tool, pumping fluid into the subsurface layer and stopping pumping said fluid once the formation is fractured until a pseudo-radial or pseudo-linear flow is reached. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

Claims

1. A method for calculating transmissibility of a subsurface layer using a downhole tool having two packers, a pump, a pressure gauge and means for recording a value indicating the volume of fluid pumped into the formation, wherein said downhole tool:

isolates an interval of said subsurface layer;

pumps fluid into said isolated interval;

stops pumping after said subsurface layer has fractured; and

records the pressure in said isolated interval for a sufficient period of time to allow the transmissibility of said subsurface layer to be calculated.

2. A method as described in claim 1, wherein said subsurface layer has a permeability on the order of one tenth of a millidarcy (0.1 md) or lower.

3. A method as described in claim 1 wherein the borehole pressure is recorded until a pseudo-radial or pseudo-linear flow is reached.

4. A method as described in claim 1 wherein pore pressure is calculated.

5. A method as described in claim 1 wherein permeability is estimated.

6. A method for calculating transmissibility of a subsurface layer comprising the steps of:

i. positioning a formation tester at said subsurface layer,

ii. activating the packers to isolate an interval,

iii. pumping fluid into the formation through the space in between the packers,

iv. monitoring borehole pressure,

v. stopping pumping once the formation has been fractured,

vi. monitoring borehole fluid for the period of time needed to achieve pseudo-radial or pseudo-linear flow; and

vii. use modeling software to calculate transmissibility of said subsurface layer.

7. A method as described in claim 6 wherein pore pressure is calculated.

8. A method as described in claim 6 further comprising the step of measuring the height of the fracture.

9. A method for calculating transmissibility of a subsurface layer comprising:

modeling borehole pressure data values that have been recorded from the time said subsurface layer was fractured by isolating said subsurface layer with a downhole tool, pumping fluid into said subsurface layer and stopping pumping said fluid after the formation is fractured until a pseudo-radial or pseudo-linear flow is reached.

10. A method as described in claim 9 wherein pore pressure is also calculated.

11. A method as described in claim 9 further comprising the step of measuring the height of the fracture.