Method and apparatuses for logging hydrocarbon reservoirs
AssigneeReeves Wireline Technologies Limited
InventorsCharles Alexander Pereira, James Roger Samworth
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Abstract
A method, of logging a borehole, for use in a cased oil well for detecting the gas/oil or water/oil contact in a hydrocarbon reservoir, using a neutron capture technique to detect one or more properties of fluid includes comparing the count rates from two or more radiation detectors spaced at respective first and second distances from an isotopic source of continuous neutron radiation. The contact detection criteria are arranged to be substantially independent of borehole fluid characteristics. Apparatus (10) for carrying out the method includes a logging tool (10) having an isotopic source (16) and two spaced detectors (17,18).
Claims20
A method, of logging a borehole, for use in a cased oil and gas wells for detecting the gas/oil or water/oil contact in a hydrocarbon reservoir, using a neutron capture technique to detect one or more properties of fluid by comparing the count rates from two or more neutron radiation detectors spaced at respective first and second distances from an isotopic source of continuous neutron radiation, the method including the steps of, at one or more locations along a said borehole, independently determining the properties of the borehole fluid and the formation fluid to define contact detection criteria and hence establish the location of the contact in a way that is unaffected by the borehole fluid and formation fluid chloride contents.
A method, of logging a borehole, for detecting a selected one of a gas/oil and water/oil contact in a cased well, said contact being the relative proportions of each first and second fluids detected in the formation fluid and the borehole fluid of the well, comprising the steps of:
- using a radiation source producing neutrons to irradiate the well from a tool lowered thereinto;
- detecting said radiation with at least two detectors on said tool with one detector being closer to said source and the other being farther from said source, said detectors providing a near count and far count, respectively;
- logging a first well having known contact conditions, to collect near and far count data over the range of percentage proportions for each fluid and generating a characteristic plot therefrom defining the range of contact values for each fluid in the foundation and borehole whereof said plot is a plot of near count rates vs. far count rates and renders a closed four-sided, four-corner plot;
- logging a well of unknown contact conditions to determine near and far count data;
- and
- interpolating said unknown contact conditions data with respect to said characteristic plot to determine the contact values of said formation and borehole fluids.
Dependencies are inferred from the claim text.