Well Deviation Problem: A Case Study in an Iranian Gas Well Drilling
Keywords:Well deviation, BHA tendency, Torque and drag analysis, Drilling stabilizer placement, Drilling parameters.
Unexpected well deviations can bring the drilling projects lots of financial and technical damages. As a result, investigation of the Bottom Hole Assembly (BHA) tendency and prediction of the probable mechanical behavior of the drilling string, especially when a new configuration is running in the hole, is critical to prevent unexpected failures. In this paper, a drilling project in an Iranian gas field which ended in a catastrophic well trajectory is going to be studied in more detail. Here, we try to answer three main questions. The reasons for the unusual well trajectory and the possibility of predicting this behavior is the first issue. The second question is about the signs of this failure during the operation and the ways that we could detect it earlier. In the third question, the alternative plans that can prevent this problem are examined by studying different BHA configuration and drilling parameters. The major sources of our information are the daily drilling reports, well log data, related published articles, and numerical simulations in WELLPLANTM software of Landmark package. According to the simulation results, BHA design is one of the most effective factors in this case study and its effect could be predicted using BHA tendency analysis before starting the drilling operation. During drilling of this well, some anomalies have been observed in drill string mechanical parameters such as hook load, rotation torque and up and down drags. Simulation of torque and drag charts for some probable well trajectories shows completely different trends for the expected well trajectory and the actual one. The observed data during the drilling operation are similar to the ones simulated for a highly deviated well and are completely unlike the trend of the near-vertical well path. Hence, it was possible to detect the wrong situation if we had simulated the mechanical behavior of the drill string and compare it with the actual observations during the operation. Finally, examination of various BHAs reveals that using an in-gauge stabilizer 10 meters above the bit instead of the one that is 20 meters above the bit could provide better well path control. It is completely obvious from the different build and walk rates which resulted in about 19 different BHA configurations. Moreover, the suggested BHAs demonstrate a good tolerance in case of changing WOB in the desired range. In the end, besides from being careful and alert during the drilling operation, the application of credible drilling simulators is strongly recommended in order to prevent unforeseen situations and also to be prepared if some happen.
Murphey CE, Cheatham JB. Hole Deviation and drill String Behaviour, SPE-1259. Society of Petroleum Engineers Journal. 1966 March; 6(1): p. 44-55. https://doi.org/10.2118/1259-PA
Stanley C. Recent Trends in Controlling Hole Deviation, API62015. In Drilling and Production Practice; 1962; New York. p. 15-27.
Lubinski A. A Study of the Buckling of Rotary Drill String. In Drilling and Production Practices (API-50-178); 1950; New York.
MacDonald GC, Lubinski A. Straight-Hole Drilling in CrookedHole Country. In Drilling and Production Practice (API-51- 080); 1951; New York.
Lubinski A, Woods HB. Factors Affecting the Angle of Inclination and Dog-Legging in Rotary Boreholes. In Drilling and Production Practice (API-53-222); 1953; New York.
Woods HB, Lubinski A. Practical Charts for Solving Problems on Hole Deviation. In Drilling and Production Practice (API54-056); 1954; New York.
Lubinski A, Woods HB. Use of Stabilizers in Controlling Hole Deviation. In Drilling and Production Practice (API-55-165); 1955; New York.
Lubinski A. Maximum Permissible Dog Legs in Rotary Boreholes, SPE-1543. Journal of Petroleum Technology. 1961 February; 13(2). https://doi.org/10.2118/1543-G
Bogy DB, Palsay PR. Buckling of Drill Pipe in an Inclined Hole. Journal of Engineering for Industry. 1964 May; 86(2): p. 214-220. https://doi.org/10.1115/1.3670492
Huang T, Dareing DW. Buckling and Frequencies of Long Vertical Pipes. Journal of Engineering Mechanics Division of the ASCE. 1969 February; 95(1): p. 167-182.
Fischer FJ. Analysis of Drill Strings in Curved Boreholes, SPE-5071-MS. In Society of Petroleum Engineers of AIME; 1974; Houston, Texas. https://doi.org/10.2118/5071-MS
Nicholson RW. Analysis of Constrained Directional Drilling Assemblies. PhD Dissertation. Tulsa: University of Tulsa, department of Petroleum Engineering; 1972.
Wolfson L. Three-Dimensional Analysis of Constrained Directional Drilling Assemblies in Curved Hole. MSc Thesis. Tulsa: The University of Tulsa, Department of Petroleum Engineering; 1974.
Millheim K, Jordan S, Ritter CJ. Bottom-Hole Assembly Analysis Utilizing the Finite Element Method, SPE-6057-PA. Journal of Petroleum Technology. 1978 February; 30(2). https://doi.org/10.2118/6057-PA
Millheim KK, Apostal MC. The Effect of Bottom Hole Assembly Dynamics on the Trajectory of a Bit. Journal of Petroleum Technology. 1981 December; 33(12): p. 2323- 2339. https://doi.org/10.2118/9222-PA
Dunayevsky VA, Judzis A, Mills WH. Onset of Drill String Precision in a Directional Borehole, SPE-13027. In 59th Annual Technical Conference of the SPE; 1984; Houston, Texas. https://doi.org/10.2118/13027-MS
Dunayevsky VA, Judzis A, Mills WH. Dynamic Stability of Drill Strings Under Fluctuating Weight-on-Bit, SPE-14329. In 60th Annual Technical Conference of the SPE; 1985; Las Vegas.
Baird JA, Apostal MC, Wormley DN. Analyzing the Dynamic Behavior of Some Typical Rotary Bottom Hole Assemblies During Start Up. Geothermal Resources •Council Transactions. 1985; 9(1).
Baird JA, Caskey BC, Wormley DN, Stone CM. GEODYN2: A Bottom Hole Assembly- Geological Formation Dynamic Interaction Computer Program, SPE-14328. In the 60th Annual Technical Conference of the SPE; 1985; Las Vegas. https://doi.org/10.2118/14328-MS
Baird JA, Apostal MC, Wormley DN. Phase2 Theoretical Description- A Geological Formation - Drill String Dynamic Interaction Finite Element Program (GEODYN2). Theoretical Description. Sandia Laboratories; 1986. Report No.: SAND86-7084.
Brakel JD, Azar JJ. Prediction of Wellbore Trajectory Considering Bottomhole Assembly and Drill Bit Dynamics, SPE-16172. In SPE/IADC Drilling Conference; 1987; New Orleans, LA.
Brett JF, Gray JA, Bell RK, Dunbar ME. A Method of Modelling the Directional Bahavior of Bottomhole Assemblies Including Those with Bent Subs and Downhole Motors, SPE4767. In IADC/SPE Drilling Conference; 1986; Dallas, Texas. https://doi.org/10.2118/14767-MS
Williams JB, Apostal MC. An Analysis of Predicted Wellbore Trajectory Using a Three-Dimensional Model of a Bottomhole Assembly with Bent Sub, Bent Housing ans Eccentric Contact Capabilities, SPE-19545. In the 64th Annual Technical Conference and Exhibition of SPE; 1989; San Antonio, Texas. p. 273-285. https://doi.org/10.2118/SPE-19545-MS