Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Earth science
Reexamination Certificate
2001-09-28
2004-05-04
Barlow, John (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Earth science
C175S024000
Reexamination Certificate
active
06732052
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to systems for drilling oilfield wellbores and more particularly to the use of a neural network to model dynamic behavior of a non-linear multi-input drilling system.
2. Description of the Related Art
Oilfield wellbores are formed by rotating a drill bit carried at an end of an assembly commonly referred to as the bottom hole assembly or “BHA.” The BHA is conveyed into the wellbore by a drill pipe or coiled-tubing. The rotation of the drill bit is effected by rotating the drill pipe and/or by a mud motor depending upon the tubing used. For the purpose of this invention, BHA is used to mean a bottom hole assembly with or without the drill bit. Prior art bottom hole assemblies generally include one or more formation evaluation sensors, such as sensors for measuring the resistivity, porosity and density of the formation. Such bottom hole assemblies also include devices to determine the BHA inclination and azimuth, pressure sensors, temperature sensors, gamma ray devices, and devices that aid in orienting the drill bit a particular direction and to change the drilling direction. Acoustic and resistivity devices have been proposed for determining bed boundaries around and in some cases in front of the drill bit.
The operating or useful life of the drill bit, mud motor, bearing assembly, and other elements of the BHA depends upon the manner in which such devices are operated and the downhole conditions. This includes rock type, drilling conditions such as pressure, temperature, differential pressure across the mud motor, rotational speed, torque, vibration, drilling fluid flow rate, force on the drill bit or the weight-on-bit (“WOB”), type of the drilling fluid used and the condition of the radial and axial bearings.
Operators often tend to select the rotational speed of the drill bit and the WOB or the mechanical force on the drill bit that provides the greatest or near greatest rate of penetration (“ROP”), which over the long run may not be most cost effective method of drilling. Higher ROP can generally be obtained at higher WOB and higher rpm, which can reduce the operating life of the components of the BHA. If any of the essential BHA component fails or becomes relatively ineffective, the drilling operation must be shut down to pull out the drill string from the borehole to replace or repair such a component. Typically, the mud motor operating life at the most effective power output is less than those of the drill bits. Thus, if the motor is operated at such a power point, the motor may fail prior to the drill bit This will require stopping the drilling operation to retrieve and repair or replace the motor. Such premature failures can significantly increase the drilling cost. It is, thus, highly desirable to monitor critical parameters relating to the various components of the BHA and determine therefrom the desired operating conditions that will provide the most effective drilling operations or to determine dysfunctions that may result in a component failure or loss of drilling efficiency.
Physical and chemical properties of the drilling fluid near the drill bit can be significantly different from those at the surface. Currently, such properties are usually measured at the surface, which are then used to estimate the properties downhole. Fluid proerties, such as the viscosity, density, clarity, pH level, temperature and pressure profile can significantly affect the drilling efficiency. Downhole measured drilling fluid properties can provide useful information about the actual drilling conditions near the drill bit.
Recent advancements in the field of drilling dynamics occurred with the development and introduction to the industry of “smart” downhole vibration Measurement-While-Drilling (MWD) tools. These advanced MWD tools measure and interpret drillstring vibrations downhole and transmit condensed information to the driller in real time. The basic philosophy of this approach is to provide the driller with real-time information about the dynamic behavior of the BHA, so that the driller may make desired corrections. The time interval between determining a dysfunction and the corrective action was still significant.
A multi-sensor downhole MWD tool acquires and processes dynamic measurement, and generates diagnostic parameters, which quantify the vibration related drilled dysfunction. These diagnostics are then immediately transmitted to the surface via MWD telemetry. The transmitted information may be presented to the driller in a very simple form, (for example, as green-yellow-red traffic lights or color bars) using a display on the rig floor. Recommended corrective actions are presented alongside the transmitted diagnostics. Based on this information, and using his own experience, the driller can then modify the relevant control parameters (such as hook load, drill string RPM and mud flow rate) to avoid or resolve a drilling problem.
After modifying the control parameters, and after the next portion of downhole data is received at the surface, the driller observes the results of the corrective actions using the rig floor display. If necessary, the driller might again modify the surface controls. This process may tentatively continue until the desired drilling mode is achieved.
The commercial introduction of advanced MWD drilling dynamics tools, and the Closed-Loop vibration control concept, has resulted in the need for a more reliable method of generating the corrective advice that is presented to the driller. It is necessary to develop a reliable method of selecting the appropriate drilling control parameters to efficiently cure observed dynamic dysfunctions. This implies the development of a method to predict the dynamic behavior of the BHA under specific drilling condition.
Drilling dynamic simulators have been developed based on a pseudo-statistical approach. A system identification technique was used to implement this concept. This approach requires the acquisition of downhole and surface drilling dynamics data, along with values of the surface control parameters, over significant intervals of time. This information is then used to create a model that, to some degree, simulates the behavior of the real drilling system. Although this approach represented a significant step forward in predictive drilling dynamics modeling, it achieved only limited success, as it was appropriate only for the identification of linear systems. The behavior of a drilling system, however, can be significantly non-linear. Therefore other methods of modeling the dynamic behavior of the drilling system to achieve the necessary degree of predictive accuracy are desirable.
Real-time monitoring of BHA and drill bit dynamic behavior is a critical factor in improving drilling efficiency. It allows the driller to avoid detrimental drillstring vibrations and maintain optimum drilling conditions through periodic adjustments to various surface control parameters (such as hook load, RPM, flow rate and mud properties). However, selection of the correct control parameters is not a trivial task. A few iterations in parameter modification may be required before the desired effect is achieved and, even then, further modification may be necessary. For this reason, the development of efficient methods to predict the dynamic behavior of the BHA and methods to select the appropriate control parameters is important for improving drilling efficiency.
The present invention addresses the above noted problems and provides a drilling apparatus that utilizes a Neural Network (NN) to monitor physical parameters relating to various elements in the drilling apparatus BHA including drill bit wear, temperature, mud motor rpm, torque, differential pressure across the mud motor, stator temperature, bearing assembly temperature, radial and axial displacement, oil level in the case of sealed-bearing-type bearing assemblies, and weight-on-bit (WOB).
SUMMARY OF THE INVENTION
The present invention provides an apparatus and method for automated dril
Dashevskiy Dmitriy
Dubinsky Vladimir
Krueger Volker
Macdonald Robert P.
MacPherson John D.
Baker Hughes Incorporated
Le Toan M
Madan Mossman & Sriram P.C.
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