Wells in Tighter Formations Can Be Tested for Boundaries
By Dr. Fred L. Goldsberry, P.E. President of Wavex Inc. |
Thu, 27 Aug 2009
DRC and WAVEX, Inc. teamed up to save drilling an unnecessary well for a South Texas Operator. We often hear from clients that it is not practical to test wells in areas that have tighter formations. While it takes a bit longer to test wells with permeabilities in the 1 to 2 Md. range the results are as accurate as in higher permeability formations. The time to test a given distance is a function of the square root of hydraulic diffusivity. Porosity, fluid viscosity, and compressibility are contributors along with permeability.
WAVEX (wave exploration) is a patented process based upon a radial capillary and wave mechanics model. The method recognizes boundary contacts as discrete events in the data set. These events when placed into a general energy model produce information about individual reservoir boundaries. These boundary images are then assembled into a most probable map. This map is produced solely from pressure, fluid and log information without reference to the clientís geologic map. WAVEX Energy Maps are relative images; that is, the direction of the boundaries with respect to north and south are not known. When the image overlays the geologic map, this is a completely independent confirmation of the geologic mapping. As a bonus, the method measures gas inplace much like a transient P/z.
The hurdle is to deal with the time required to acquire the desired result. In this case the operator was concerned about the necessity of drilling a second well to drain the reservoir. Generally speaking, if we can see and map the reservoir, the operator can effectively drain the reservoir. Often in deep hot areas it is difficult to produce clear seismic images. The test required less than 30 days to execute as can be seen in the data plot below. The surface data was accurately converted by DRC to downhole conditions.
The data set shows four clear-cut contacts, which were used in the WAVEX Energy Model to produce the following image of the reservoir.
The next image is an overlay of the WAVEX Energy Map on top of the Seismic Map. Both are derived from different sets of wave mechanics yet the similarity of the overlay of the energy map to the seismic map is striking.
The questions most often asked are ěCan you test a well accurately from the surface?î and ěCan you produce a blind reservoir image from pressure data?î The answer is we just did!
Summary
No new well was drilled due to a determination of effective drainage from the single well. The entire process involves a 30-day SPIDR Rental and a WAVEX analysis. The sum total cost is less that the price of a spinner survey. In this process it is not necessary to run a tool string into the hole. Keep in mind that test planning is free. If you would like to learn more about WAVEX please contact us at drc@spidr.com or Dr. Fred Goldsberry at wavex@sbcglobal.net.
