Development of an Expert System for Solids Control in Drilling Fluids
Authors: Pandey Vibhas , Osisanya S.O. 
Published: March 2010

An efficient solids control procedure or mechanism is one of the keys to drilling optimization. This can be achieved by employing proper solids control equipment while drilling is in progress. This paper presents an expert system that is developed for the selection of proper solids control equipment. An expert system is an interactive computer based tool that simulates the thought process of human experts to solve complex problems in a specific domain. The key stages in the development include: problem definition and analysis, knowledge acquisition (involving consultation with experts), knowledge-base development, interface development, and finally input and output data presentation.

The expert system developed has four important modules. The first module is based on an extensive survey of the literature available on the subject to date. Upon input from its user, it suggests the best possible combination of solids control equipment that is compatible with the drilling parameters. The second module helps the user in carrying out density control calculations pertaining to solid control. The third module is in a text mode, and describes the solids control equipment commonly installed on the rigs, along with the criterion involved in their application. The fourth module allows the user to note down his experience pertaining to any particular situation he may have come across. This can be of help to him, or to any other user who may be faced with a similar situation later.

This paper presents the methodology and various examples under these four modules to demonstrate field related applications. The salient features on this expert system are its " userfriendliness" and ability to constantly self-improve itself constantly by maintaining a " dynamic memory." A listing of the program is included in this paper to allow readers to validate the technique and gain benefit of the paper. At the rig site, this system will allow the user to familiarize himself with the solids control equipment. This will help in obtaining the best possible equipment arrangement for effective solids control and various density control calculations.

Introduction

Selection of the right kind of drilling fluid is essential for economic drilling of wells. During drilling, drilled solids or cuttings generated at the bit, mix and interact with the initially formulated drilling fluid, and bring about changes in its density, rheology, and other properties of the fluid. These factors, in turn, are determined by such interacting variances as lithology, fluid properties, penetration rate and the wellbore geometry.

Several studies(1-8) mention the disadvantages related to poor solids removal while the drilling is in progress. These include higher density, higher viscosity, higher filtration rate, and higher filter cake thickness. Practically, this means lower rates of penetration, reduction in bit-bearing life, higher torque and drag and more chances of stuck pipe. Definitely, this is uneconomical for drilling operations.

A large number of variables are often involved in deciding the type of solids control equipment that has to be employed for a particular kind of drilling situation.