Systems and methods for monitoring changes in a formation while dynamically flowing fluids
Methods and systems for measuring neutron sigma of downhole reservoir as a function of time for a predetermined testing volume are disclosed. The methods and systems of the present invention analyze the testing volume while maintaining the formation in the testing volume in an unchanged and undamaged state and while dynamically flowing fluids in and out of the testing volume. The systems and methods of the present invention are especially important in determining petrophysical information about the reservoir as well as the in-situ effect of substances on enhanced oil recovery.
1. A method for measuring a parameter within a formation, the formation having a first fluid comprising a plurality of constituents therein,
comprising the steps of:
positioning and releasably fixing a formation tester at a predetermined depth within a well bore in the formation;
sealing a portion of a wall of the well bore and providing a sealed area;
positioning a fluid communication device having at least one orifice positioned within the sealed area;
directing a neutron energy burst into the formation;
sensing a return neutron signal from a testing volume proximate the sealed area in the formation;
obtaining an apparent sigma of the testing volume;
correcting the apparent sigma in relation to the testing volume to obtain an intrinsic sigma for the testing volume;
obtaining a plurality of sigma values from the intrinsic sigma for the plurality of constituents; and
determining the parameter in the testing volume using the plurality of sigma values.
2. The method of claim 1 further comprising pumping the first fluid from the formation into the testing volume and into the at least one orifice and into the formation tester.
3. The method of claim 2 wherein the determining the parameter is selected from a group of parameters consisting of contamination, gas to oil ratio, porosity, bubble point, saturation, or any combination thereof.
4. The method of claim 3 further comprising determining at least one of a mobility, an oil permeability, a water permeability, a capillary pressure, or a fractional flow with respect to saturation.
5. The method of claim 2 further comprising pumping a second fluid from the formation tester into the testing volume.
6. The method of claim 5 wherein the second fluid is comprised of an enhanced oil recovery fluid.
7. The method of claim 6 wherein the apparent sigma for the testing volume includes a value indicative of an effectiveness of the enhanced oil recovery fluid.
8. The method of claim 1 wherein the determining the parameter is determining a mineral content of the testing volume.
9. The method of claim 8 wherein the mineral content is indicative of aluminum.