Expert System For Directional Drilling Process Control
Authors: Mamedbekov O.K. , Gasimov A.A. 
Published: December 2007

Abstract
Directional well drilling Expert system was developed in the ASPA's (Azerbaijan State Petroleum Academy) division of directional and horizontal drilling. Expert system can help oil companies solve directional borehole deviation control problems and increase efficiency of drilling process. The Expert system provides receiving reliable on-line information, carrying out different calculations, giving course correction and bottomhole assembly parameters recommended in the current technological situation. It is used by SOCAR's (State Oil Company Azerbaijan Republic) drilling engineers in the office as well as at the well site.

Introduction
At present, directional drilling from the platforms constitutes the main footage of offshore drilling. The number of directional wells that can be drilled from the offshore platform may be several dozen. The modern offshore platforms are equipped by two drilling rigs which provide drilling two new wells and oil production from the wells already drilled simultaneously. The big number of wells and small distance between their surface locations (2.0–2.5m) make possible borehole intersection with potential loss of life and equipment.
Moreover, the deviation of the borehole from the planned well path should be adjusted with correction run. As a result, there is a risk of doglegs, which can later cause different hole problems and drilling tool failures.
Therefore, the reliability of directional borehole deviation process control is one of the main problems in multiple well drilling.
Fig.1 shows the horizontal projection of multiple well structure drilled in the Guneshli field, Caspian Sea, Azerbaijan.

Directional Drilling Software
Complexity of directional drilling requires more detailed planning to lessen cost and risk. Besides, the intensification of the modern drilling process requires on-line control decision-making while drilling. The use of computers is therefore critical to successfully plan and drill directional wells. The use of software programs greatly increases the efficiency of the drilling process and allows the engineers to more accurately calculate drilling parameters, optimize drilling operations and prevent potential well problems.
The directional drilling software passed several steps of development: programs for calculation of directional drilling different technological processes, software for directional well planning and control, directional drilling computer-aided control system.
The directional drilling software is generally based on statistical and analytical models.
Statistical models are a result of field data processing. These models cannot be used to control the drilling process of wells drilled in a field other than the one in which the data were taken. On the other hand, definite errors of the field data affect the statistical models accuracy. Therefore, the results of calculations based on these models frequently does not coincide with drilling practice.
Analytical models include a complex influence of technical and geological factors that affect the deviation process of a directional well. These models use empirical coefficients (such as formation and bit anisotropy index, friction factor and others), which are determined statistically. Therefore, the effective application of analytical models is possible if these coefficients are available.

Directional Drilling Expert System
Directional drilling practice has shown that the drilling process in many cases has been carried out with insufficient input information that can cause the uncertainty of control conditions which often have nonprobabilistic, but fuzzy character. Therefore, the efficiency of drilling process control is based on the complex approach of making decisions and using modern methods of complicated and uncertain systems investigation.
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