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. • 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.
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.
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. • 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 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 equipmentand technology, that reduces lost time for mud conditioning/circulation and extra expenses.
Thank you for your attention! Shteryo