Date Submitted: 08.2002.
Technical Area: Hole Cleaning, Drilling Hydraulics, Drilling Fluid Technology, and Well
Planning.
Sponsor: UNOCAL.
Title: Apparatus and method to test drilling fluid stability - Barite Sag Tester.
Submitted by: Mining and Geology University, Dept. of Drilling and Oil and Gas Production,
Sofia – 1700, BULGARIA, tel. +359 2 9627220 ext. 463.
Principal Investigator (s): Shteryo K. Lyomov / lyomov@mgu.bg
/ Lubomir G. Gerov / gerov@mgu.bg
/ Nikolay Nenkov.
Business Impact: Predicting drilling mud stability with respect to barite sag and cuttings transport in inclined/horizontal hole sections always has been ultimate goal of the recent drilling fluid and drilling hydraulics technology development. This issue has considerable economical impact lately with the “invasion” of the synthetic OBM /olefins, esters, starch and polyglycerol drilling fluids/, which generally show low tixotropy. The HPHT conditions of drilling in some fields make the problem even more pronounced even for some WBM. The existing methods and tools are unable to provide trustworthy input in this critical issue. Using computer programs
/HYDRAUL, MUDMAN and other/ and indirect parameters such as low shear rate rheology, viscous - elastic mud properties, in order to predict barite sag often lead to erroneous results and thus to loss of time and extra expenses. The field practice has a lot of case histories proving the above statement. As it might be concluded barite sagging is an “expensive slipping” problem and the main point/focus in its solution is the ability to be predicted; an edge where the known solution fail or provide misleading results.
The successful project will result to a development of an Apparatus and Method to Test
Drilling Fluid Stability – Sag Tester

.
It uses pressure measurement to detect the drilling mud instability with respect to barite sag and cutting bed formation. The idea, of the suggested tool (Sag Tester

), is further development of the work published in JCPT by P. Skalle, K.R.
Backe, S.K. Lyomov et. al.
“ Barite Segregation in Inclined Boreholes
” paper 97-76. This new tool can be used at the rig site and in the laboratory. It is aimed to help field and research personnel to evaluate drilling fluids. At the rig site drilling mud testing, with the Sag Tester

, will help mud treatment before trip and/or during drilling. In laboratory conditions investigations can be performed and thus the composition of drilling mud and drilling hydraulics program can be optimized. We believe that with the Sag Tester

also mud’s cutting suspending ability can be measured too.
Technical Objectives: This project will be focused on the problem of predicting barite sagging.
It is aimed to provide the drilling industry with tool /apparatus and method/ for direct measurement mud instability that could cause conditions for sagging. Complete set of methodologies for the application of the Sag Tester

will be developed. In collaboration with the sponsors, critical evaluation of their field/lab applicability will be done. Based on the

success of the technology aggressive marketing of the new technology can be done. The main goals of this research project work are:
1) To design and construct suitable equipment (Sag Tester

) for prediction the drilling mud stability;
2) To develop software and establish criteria for evaluation of the sagging hazard;
3) To verify/debug the mechanical firmware, and software (sensitivity, accuracy, reliability) at lab and field conditions;
4) Determine best field practice;
5) Commercial promotion.
Methodology: The project will be divided into two phases:
1) Pre–project phase, which includes work for development of the equipment set up Sag
Tester

- hardware and software. Tuning the equipment – sensitivity, accuracy and reliability, software debugging, etc. Testing different types drilling fluids and setting of initial criteria for drilling fluid stability evaluation. Specific experimental facilities will be used for this purpose.
2) Project phase – this phase includes work to develop/produce industrial Sag Tester

and field implementation and testing. To organizing study seminars for the sponsoring companies. Each company involved in the JIP will get a field Sag Tester

and implement it on the rig site. The gathered field date will be used for fine tuning and adjusting the evaluation criteria.
3) Marked promotion of the new technology will also be done in this phase.
Deliverables: The participants of this JIP will be provided with the developed equipment - Sag
Tester

and software – Sag Soft

. The software will predict the drilling mud stability with respect to barite sag. Limits for trouble free drilling in inclined/horizontal hole sections will be set based on the measurements. A final report will summarize the results from lab development and field-testing of the new tool.
Startup Date: 2003.
Project Duration: Pre-project:
Project:
12 months,
12 months.
Project Cost: Pre-project
Project
64 000 USD,
175 000 USD.
Cost per Participant: Pre-project:
Project:
4 participants 16 000 USD each
5 participants 35 000 USD each
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