Beam-Steerable Mechanical Sensing of In-Situ Rock Properties using Controlled Drilling Vibrations

Physical Sciences : Petroleum

Available for licensing

Inventors

  • Carlos Torres-Verdin , Petroleum and Geosystems Engineering
  • Roman Shor , Petroleum Engineering
  • Eric van Oort , Petroleum and Geosystems Engineering

Background/unmet need

Precise knowledge of rock mechanical properties in the subsurface is of utmost importance to the hydrocarbon exploration and production industry. These properties are used to improve drilling operations, design well completions, and stimulate hydrocarbon production via hydro-fracturing operations, for instance.

Many technologies exist to estimate rock properties prior to drilling, such as the use of seismic amplitude data, drilling operations through logging while drilling (LWD), or measuring while drilling (MWD) tools. Rock properties can also be estimated after drilling using wireline logging operations. Previous work investigated the use of drilling noise stemming from the rock failure process as an acoustic source to infer reflective surfaces ahead, above, or below the bit or to estimate rock mechanical properties.

However, such previous technologies and methods suffer from low spatial resolution and low accuracy either because of the remote detection of rock mechanical properties (via, for instance, seismic amplitude measurements) or because the estimated rock properties no longer reflect original (in-situ) conditions due to the drilling process itself. 

Invention Description

Researchers at The University of Texas at Austin have proposed an invention that utilizes a controlled input signal, an axial or torsional source in the drillstring that is either at the surface or near the bit, to excite a broad range of mechanical harmonics of the drilling system. A method is then proposed to segment the recorded mechanical harmonics into those of the drillstring structure itself and those of the bit-rock interaction. The former can be estimated and are a function of the geometry of the drilling system, while the latter ones may then be used to estimate the mechanical properties of rocks penetrated by the drill bit.  

Benefits/Advantages

  • Improved drilling efficiency through better knowledge of rock formation strength
  • Improved subsurface rock and fluid description for efficient production management
  • Better reservoir models enabled to improve estimation of recoverable hydrocarbon reserves and management of fluid-production techniques

Features

  • Increased signal-to-noise ratio of measurements
  • Mechanical harmonics of the drillstring allowed to be estimated and removed from measurements
  • Remaining harmonics may be used to estimate rock mechanical properties that accurately represent those of rocks under actual subsurface (in-situ) conditions
  • Tests can be done frequently during drilling, processed in real time, and may then be used to continuously estimate downhole rock mechanical properties

Market potential/applications

The target markets for the invention are the operators in the oil and gas industry together with service companies that provide geotechnical and drilling services at the wellsite. Well logging and formation evaluation is a $15B business worldwide (2015 figures) and Measurement while Drilling (MWD)/Logging While Drilling (LWD) services are used on a majority of land wells in the United States. Virtually all operators would be interested in a nonintrusive test which could be conducted before or after performing a drilling connection (every 45 to 90 feet of wellbore drilling) to offer accurate and reliable estimates of downhole mechanical properties of rocks. 

Development Stage

Proof of concept

IP Status

  • 1 PCT patent application filed
  • 1 U.S. patent application filed