Water injection profiling
AssigneeTexaco Inc.
InventorDan M. Arnold
Life of this patent
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Abstract
Water injection profiling of a well by nuclear logging is disclosed. A dual detector sonde with a high energy neutron source and a spinner flowmeter is oriented and positioned above and below perforations in the casing of an injection well to monitor upward and downward flow, respectively, of injection water. The water is irradiated by the neutron source and resulting gamma ray production is sensed as the activated water flows by the spaced detectors. Count rate data is reduced and analyzed in terms of two energy windows to obtain linear flow velocities for water flow behind the casing. Fluid flow within the casing is measured by means of the spinner flowmeter. Volume flow rates are determined for upward and downward flow, and horizontal volume flow into the surrounding formations is calculated.
Claims20
A method for determining the characteristics of flow of injection water in and beyond a known size cased well borehole having casing perforations at one or more levels within the well comprising the following steps:
- (a) providing a well tool having a source of radiation and at least two detectors longitudinally spaced from said source and each other, and having flowmeter means;
- (b) positioning said well tool below a level of casing perforation with said radiation source above said detectors;
- (c) operating said flowmeter means to monitor fluid flow within said casing below said perforation level, and generating signals indicative of the linear velocity of said fluid flow;
- (d) irradiating the borehole environs, including injection water being forced into the borehole, by radiation from said radiation source;
- (e) detecting radiation from the activated injection water by operation of said detectors and generating signals representative thereof;
- (f) distinguishing count rate data from at least one of said detectors according to two energy ranges of detected radiation;
- (g) combining said count rate data and said linear flow velocity obtained by operation of said flowmeter means according to a first predetermined relationship to derive an indication of the linear flow rate of said activated injection water downwardly behind said casing below said perforation level;
- (h) positioning said well tool above said level of casing perforation with said radiation source below said detectors, and repeating steps (d) through (f);
- and
- (i) combining said count rate data according to a second predetermined relationship to derive an indication of the linear flow rate of said activated injection water upwardly behind said casing above said perforation level.
A method of determining the characteristics of flow of injection water in and beyond a known size cased well borehole having casing perforations at one or more levels within the well comprising the following steps:
- (a) providing a well tool having a source of neutrons of sufficient energy to cause the nuclear reaction O.sup.16 (n,p)N.sup.16, at least two gamma ray detectors longitudinally spaced from said source and each other, and having spinner flowmeter means;
- (b) positioning said well tool below a perforation level with said detectors below said source in a down-flow configuration, and positioning said well tool above a perforation level with said detectors above said source in an up-flow configuration;
- (c) with said well tool in said down-flow configuration and in said up-flow configuration, repetitively irradiating the borehole environs, including said injection water being forced into said well, with bursts of high energy neutrons from said source, detecting, subsequent to each neutron burst, at each of said detectors gamma rays caused by the decay of the unstable isotope nitrogen 16, and generating signals representative thereof;
- (d) distinguishing count rate data from said detectors according to two energy ranges of detected gamma rays;
- (e) with said well tool positioned below and above said perforation level, operating said spinner flowmeter means to obtain values of the linear flow rate of injection water flowing downwardly within said casing below and above, respectively, said perforation level;
- (f) combining said count rate data, acquired with said well tool in said down-flow configuration, according to a first predetermined relationship to derive an indication of the linear flow rate of injection water flowing downwardly behind said casing below said perforation level;
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- (g) combining said count rate data, acquired with said well tool in said up-flow configuration, according to a second predetermined relationship to derive an indication of the linear flow rate of injection water flowing upwardly behind said casing above said perforation level.
Dependencies are inferred from the claim text.