Halliburton Company

Richard L Duncan

Stephen E Tilghman

Michael J Lynch

Gilbert H Forehand

Jack C Penn

Billy W White

Ronald E Dant

Charles F VanBerg, Jr

Charles D Donaghe

Terry O Anderson

J Mark Richardson

John M Richardson

Bruce A Kaufman

A self-contained downhole apparatus for being lowered into an oil or gas well to internally record samples of at least one environmental condition comprises three body sections linearly and releasably interconnected. One of the body sections is a selected one of a plurality of transducer housing sections. The selected transducer housing section is mechanically and electrically connected to a second body section containing microcomputer-operated signal processing circuitry. The third body section contains a power supply.

Self-contained downhole gauge system

A self-contained memory gauge includes either semiconductor or magnetic core memory for retaining downhole information related to sampled parameters, such as borehole temperature and pressure. A microprocessor-based computer manages the power utilization by independently and selectably energizing and de-energizing different sections of the gauge. The magnetic core memory is tested for operability, and the addressing of the magnetic core memory is adjusted in accordance with any inoperable memory locations. Samples of the monitored environmental conditions can be taken at variable rates dependent upon software monitoring of the condition, the remaining battery life and the remaining memory capacity and in response to hardware monitored pressure changes. Each sample can be taken to a selectable resolution. A watchdog circuit monitors the microprocessor to insure that it is operating within a preselected time limit. Further, resolution counters (282) and (284), in association with multiplexer (280), provide selectable timing signals.

Self-containing downhole gauge system

In an oil well instrumentation system, the downhole sensor system is controlled by a computer which is powered-on only during sampling movement. An independent circuit, continuously powered, detects significant sensor rate-of-change values whereby the computer-sampling equipment is powered-on. A self-contained memory gauge includes either semiconductor or magnetic core memory for retaining downhole information related to sampled parameters, such as borehole temperature and pressure. A microprocessor-based computer manages the power utilization by independently and selectably energizing and deenergizing different sections of the gauge. The magnetic core memory is tested for operability, and the addressing of the magnetic core memory is adjusted in accordance with any inoperable memory locations. Samples of the monitored environmental conditions can be taken at variable rates dependent upon software monitoring of the condition, the remaining battery life and the remaining memory capacity and in response to hardware monitored pressure changes. Each sample can be taken to a selectable resolution. A watchdog circuit monitors the microprocessor to insure that it is operating within a preselected time limit.

A method of discriminating between linear and nonlinear regions of measured data is based upon two hypotheses, one of which is a hypothesis that a response is merely a result of inherent randomness and the other of which is a hypothesis that the response is a result of a true nonlinear change greater than a value M. It is also based upon a relative cost between accepting the latter hypothesis when the former is true versus accepting the former hypothesis when the latter is true. A resulting probabilistic criterion (M/2)+(.sigma..sup.2 /M) [1n(P.sub.H0 /P.sub.H1)C] is graphically implemented for deriving offset values which can be used in a specific embodiment to construct tabular values defining linear/nonlinear regions from a presumed hypothetical straight line response.

Dynamically adjustable linear data discriminator

The power-conversing apparatus includes a plurality of independently energizable electrical circuits used in receiving electrical signals from a transducer which senses an environmental condition, in processing the electrical signals, and in storing information related to the detected environmental condition. The apparatus further includes a power control circuit for continuously providing electrical power to at least one of the electrical circuits and for independently switchably providing electrical power to selectable ones of at least two others of the separately energizable circuits.

Power-conserving self-contained downhole gauge system

A method of testing a magnetic core memory includes writing a test bit to each storage location addressed by each X-drive/X-sink transistor pair and each Y-drive/Y-sink transistor pair to determine which transistor or transistors of each pair is or are inoperable. Once this determination is made, a memory status map is created designating the inoperable transistors. Thereafter, the map contents are converted into an address field for matching against a selected memory address. If the selected memory address calls for an inoperable transistor, as indicated by a comparison with the address field, this is detected and the address changed until only operable transistors are accessed.

Method of testing and addressing a magnetic core memory

A physical condition in a well bore is sampled and information taken from the sample is recorded by a method of conserving electrical energy in performing such sampling and recording. The method sequentially energizes and de-energizes a plurality of different electrical circuits within the downhole apparatus with which the physical condition is detected and in which the information is recorded. The method determines when the next sample is to be taken and, depending upon how much time remains until the next sample, de-energizes the apparatus to conserve energy.

Method of sampling and recording information pertaining to a physical

The method for controlling the rate at which a downhole logging tool samples and records a detected condition obtains three samples of the condition at three consecutive sample times and computes a prediction value for the n-th sample from the first three samples. The method compares the actual n-th sample with the predicted value and records the (n- 1)-th sample if the variance between the predicted and actual values is outside a predetermined threshold or difference. The sample rate is changed if the actual values of the samples remain within the predicted value's preselected range for more than a preselected number of samples. The sample rate interval is also increased if the battery life or memory capacity decrease below predetermined thresholds. The sample rate interval is decreased to its shortest interval if a pressure change above a predetermined threshold is detected.

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Duncan, OK, United States of America

Richard L Duncan