Drilling fluids filtration and impact on formation damage.

Amish, Mohamed Belkasem

Abstract

Three major methods that the production engineer uses to quantify formation damage in terms of well performance based on the total skin factor after drilling operations are: production logging, flow measurement and well test data. The total skin factor is used in the flow equations to estimate the production rate in wells that are affected by formation damage in order to optimise the flow system to enhance productivity. The most common source of formation damage has proved to be drilling operations. The drilling skin contributes the highest percentage of the total skin. It is however, not possible to quantify the contribution from drilling fluid to the total skin. In addition, the mechanisms of drilling fluid filtration and impact on productivity performance are not well understood. Furthermore, a satisfactory model for field applications to simulate the near-wellbore damage before drilling in terms of well performance integrated from laboratory core test analysis is still not available. In recent times, the oil industry has shown increasing awareness towards maintaining optimum well productivity through better drilling/completion fluids design. This thesis presents a new tool which can predict impact of drilling fluid filtration on formation damage and well performance from laboratory measurements carried out on samples of formation and drilling fluids. This tool is also capable of quantify the formation damage in terms of drilling skin (sd) before drilling at the design (planning stage), during drilling and post drilling (evaluation stage). In this thesis, the results of in-depth experimental research into rheology, filtration and formation damage phenomena at elevated temperature and pressure with both water-based and oil-based fluids and the relationships between them are presented. The experimental data combined with data analysis provide a better understanding of filtration and formation damage mechanisms under downhole conditions. They also provide the database for the semi-empirical mechanistic models that have been developed. These models have been combined and incorporated into a design and evaluation tool - the productivity tool, for predicting the effect of drilling fluid filtration on formation damage in terms of well productivity. The productivity tool is useful as a design and analysis tool for applications in the lab and in the field. The field applications of the productivity tool based on the drilled wells studied shows it can be used to investigate the influence of many parameters such as drilling and static operational time, overbalance pressure, temperature, reservoir permeability, types of drilling fluids, rheology design, etc. on well performance. This tool is also capable of being utilised to screen different drilling fluids desired for achieving minimum formation impairment and maximum production capacity, which can reduce the overall well cost in terms of time and operations. A number of results are presented to illustrate how the new tool can be used to evaluate the damage factor of a given fluid, specify the invaded zone skin and the depth of invasion as well as the economic implication of the skin zone on well productivity. Recommendations are also made for further work on this fascinating field of study, based on a range of new experimental techniques developed in this research.

Citation

AMISH, M.B. 2004. Drilling fluids filtration and impact on formation damage. Robert Gordon University, PhD thesis. Hosted on OpenAIR [online]. Available from: https://doi.org/10.48526/rgu-wt-2807277

• Thesis Type: Thesis
• Deposit Date: May 7, 2025
• Publicly Available Date: May 7, 2025
• DOI: https://doi.org/10.48526/rgu-wt-2807277
• Keywords: Drilling; Drilling fluids; Oil wells; Formation damage; Petroleum engineering
• Public URL: https://rgu-repository.worktribe.com/output/2807277
• Related Public URLs: https://rgu-repository.worktribe.com/output/2830062 (Supplementary data)
• Additional Information: The file accompanying this record contains the main text of the thesis, the contents of Appendices A through C, and the majority of the contents of Appendix D. The final part of Appendix D ("CD The Productivity Tool Package") was originally on a CD-ROM and has been preserved as supplementary data in a separate record: https://rgu-repository.worktribe.com/output/2830062
• Award Date: Jul 31, 2004