Prevention of Core Jamming and Damage During Coring Operations by Optimization of Drilling Parameters – Analysis of Case Studies
- Rahman Ashena (Independent Consultant) | Mosayeb Lotfi (Independent Consultant) | Andreas Nascimento (Universidade Federal do Espírito Santo UFES) | Ali Ghalambor (Oil Center Research Intl.)
- Document ID
- Society of Petroleum Engineers
- SPE International Conference and Exhibition on Formation Damage Control, 19-21 February, Lafayette, Louisiana, USA
- Publication Date
- Document Type
- Conference Paper
- 2020. Society of Petroleum Engineers
- drilling optimization, Core jamming, core damage
- 6 in the last 30 days
- 58 since 2007
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Coring is a considerably costly drilling operation, but vital to retrieve valuable sources of ground-truth data in the oil and gas industry. To justify the high cost of this operation, essentially, cores should not undergo jamming and mechanical damage. Core jamming not only indicates an unprecedented termination of the operation, but also causes severe damage to the core column already taken in the barrel. This means that the cores cannot be retrieved with sufficient key performance indicators (KPIs); thus, it would not reliably represent reservoir properties. Reaching this significant target can be ensured not only by proper design, but also by online monitoring and investigation of the drilling parameters. This investigation predicated on several case studies in the Middle East to identify the effect of imperfect decisions made by the driller. Based on the experience and observations, the paper provides practical recommendations to alleviate the impact of such negative actions.
The drilling parameters observed in the mud logging data of six coring case studies (of several runs from three wells in carbonate reservoirs) were investigated at the depth interval just prior to jamming occurrence. These parameters consist of rate of penetration (ROP), torque, weight on the bit (WOB), rotary speed (revolutions per minute, RPM), circulation rate, and standpipe pressure (SPP). In this work, a main cause of the core jamming occurrences is discussed; that is, the improper drilling parameters application, as mismanaged by the driller. Finally, as indications of jamming, sudden variations of the drilling parameters at the specified depth were investigated. Such study can contributeto the better monitoring for future coring operations.
Based on the observations in six case studies in three wells, WOB was identified as the most significant reason causing core jamming; that is, jamming occurred when the WOB was not steadily maintained on the bit probably due to the driller’s inexperience, shift change, etc. For monitoring, torque decrease, ROP decrease, and SPP variation or decrease (following initial increases) were identified as indications of core jamming. Torque showed to be a significant parameter forjamming detection when it decreases or its trend becomes completely straight, i.e., without any variations, indicating that the core head may not be in contact with the formation. Next, drilling issues during coring (such as pump failure) can contribute to subsequent jamming.
The case studies in this paper provide several observations and indications of core jamming occurrences in a limestone reservoir which can be attributed to non-optimized drilling parameters. The paper also provides several practical recommendations and measures to prevent core jamming and core damage.
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Ashena, R. & Thonhauser, G. (2018) Coring Methods and Systems, Published by Springer International Publishing, 10.1007/978-3-319-77733-7.
Ashena, R., Thonhauser, G., Ghalambor, A., Rasouli, V. & Manasipov, R. (2019) Determination of Maximum Allowable Safe Core Retrieval Rates, 189480-PA, Published online in SPE J. of Reservoir Evaluation & Engineering, 10.2118/189480-PA.
Guarisco, P., Meyer, J., Mathur, R., Thomson, I., Robichaux, J., Young, C. & Luna, E. (2011) Maximizing Core Recovery in Lower Tertiary Through Drilling Optimization Service and Intelligent Core Bit Design, SPE/IADC 140070, Presented at the SPE/IADC Drilling Conference, Amsterdam, the Netherlands, March 1-3.