Apparatus and Method To Test Drilling Fluid Stability “Sag Tester™” Associate Prof. Shteryo Lyomov, Ph.D. Mining and Geology University Department Of Drilling and Oil and Gas Production 1700 Sofia BULGARIA

Project Background Field problems associated with drilling mud stability leading to barite sagging/hole cleaning still exist. Lack of relevant/suitable equipment for direct testing of drilling mud stability at the rig site and laboratories with respect to stability (barite sagging). Gained experience in barite sag investigation.

Project Goals Pre – project. Project. Development of equipment - hardware and software; Tuning the equipment (sensitivity, accuracy, reliability and software debugging) at lab conditions and setting of initial criteria for drilling mud evaluation. Project. Development and production of industrial Sag Tester™; Conducting of training seminars for the sponsors; Field testing and implementation; Field debugging of the firmware and software; Verify mechanical/software reliability; Determining best operation practice; Commercial promotion.

Description The barite Sag Tester™ uses pressure measurements in order to evaluate drilling mud stability. The main idea is based on the Boycott effect and is a further development of the work published by P. Skalle, K. R. Backe, S. K. Lyomov et. al.* *P. Skalle, K.R. Backe, S.K. Lyomov et. al. “Barite Segregation in Inclined Boreholes” JCPT, special Vol. I, paper 97-76. Pressure measurements are used because the process of barite/particle settling influences strongly/mostly the drilling mud density.

Description, (continued) Barite Sag Tester™* Components. V – pipe; Z – pipe;  – well bore inclination; Bypass valve; Pressure sensors; Temperature sensor; D/A and control system. * Patent Pending Reg. No. 107573/BGR patent office.

Description, (continued) Drilling mud is poured into the barite Sag Tester™, while the valve is opened. This assures equal height of the mud columns in the V - pipe and Z - pipe. Then the valve is closed, pressure and temperature measurements are taken in an interval of sec/min for a period of 5 - 6 h. The difference between the pressures measured in the bottom of V - pipe and Z-pipe after a ? h time interval is a direct indication for drilling mud stability. The results from a testing two drilling mud are shown on the next 2 slides.

Description, (continued)

Description, (continued)

Mud Stability Evaluation Criteria Pressure reduction in the V – pipe dP1; Pressure reduction in the Z – pipe, dPz2; Bottom hole T and P; Borehole inclination – .

Sag Tester™ Features Simple principle of measurement; Quartz pressure sensors with high accuracy; Temperature measurement; PC based D/A and control system allows real time measurement of the drilling mud behavior; The Sag Soft™ software accounts for the influence of the borehole P, T as well as inclination – ; Simple to use at laboratory and at the rig site.

Competitive Analysis Competitors. Strengths. Limitations. sag index, sag number and sag register; software (HYDRAUL™, MUDMAN™); controlled stress and low shear rate/gel measurements. Strengths. Equipment/software exists on the market. Limitations. track the barite sag, not predict (sag index/register), impractical to use (sag number) ; not direct measurements; flow conditions in wellbore differ from these in the viscometer.

Competitive Analysis, (continued) Sag Tester™. Strengths. Uses simple principle; Direct measurement of the mud parameter related to the barite sagging - density/pressure; Easy to operate and analyze - PC/Sag Soft™ software. Limitations. New unknown equipment; Lack of field experience/data; Needs market promotion.

JIP Team/Resources Team working on the project. Project leader – Ass. Prof. Sht. Lyomov, Ph.D. Experimental work leader- Ass. Prof. L. Gerov, Ph.D. Design work leader - Prof. N. Nenkov, Ph.D. Electronics - Rhoe BG electronics Ltd. Manufacturing - University workshop, ZMM - Sofia.

JIP Team/Resources, (continued) Project resources. Pre - project 64,000 $ (4 participants 16 000 $ each) Project 175,000 $ (5 participants 35 000 $ each) Location. Mining and Geology University, Department Of Drilling and Oil & Gas Production, 1700 Sofia, BULGARIA.

Schedule Pre - project 12 months. Design 2 months Project 12 months. Building the Sag Tester set up 3 months Laboratory testing 7 months Project 12 months. Design/production industrial prototype 2 months Testing of industrial prototype 9 months Field implementation and testing 9 months Data analysis and final reporting 6 months

Expected Results Development of apparatus and method to test drilling mud stability with respect to barite sag – The Sag Tester™. Set and field prove of criteria for drilling mud evaluation. Development of software Sag Soft™ to predict mud behavior based on measurement with the Sag Tester™. Market promotion of new equipment and technology, that reduces lost time for mud conditioning/circulation and extra expenses.

Thank you for your attention! Shteryo