Sweet and Sour Fracturing : The Impact of Post-Fracture Clean-Up on H2S and the Reservoir
- A. Al-Manji (BP Oman) | A. Al-Shueili (BP Oman) | L. Orjuela (BP Oman) | D. White (BP Oman) | S. D. Kurniadi (Schlumberger Oman & Co LLC) | M. Rylance (BP Exploration)
- Document ID
- Society of Petroleum Engineers
- SPE International Hydraulic Fracturing Technology Conference and Exhibition, 16-18 October, Muscat, Oman
- Publication Date
- Document Type
- Conference Paper
- 2018. Society of Petroleum Engineers
- 4 Facilities Design, Construction and Operation, 5.6.4 Drillstem/Well Testing, 3.4.1 Inhibition and Remediation of Hydrates, Scale, Paraffin / Wax and Asphaltene, 2.5.2 Fracturing Materials (Fluids, Proppant), 2 Well completion, 5 Reservoir Desciption & Dynamics, 4.1.2 Separation and Treating, 4.1 Processing Systems and Design, 3 Production and Well Operations, 2.4 Hydraulic Fracturing, 3.4 Production Chemistry, Metallurgy and Biology, 5.6 Formation Evaluation & Management, 3 Production and Well Operations
- H2S, SRB, Hydraulic Fracturing, Sweet Reservior, Flowback
- 4 in the last 30 days
- 110 since 2007
- Show more detail
- View rights & permissions
|SPE Member Price:||USD 9.50|
|SPE Non-Member Price:||USD 28.00|
The Barik formation is a tight low-permeability conventional gas reservoir in the Sultanate of Oman comprising of a series of interbedded sandstones and shales. To achieve an efficient and economic development of this formation, the wells require the application of massive hydraulic fracturing operations, in order to achieve the required surface area and connectivity for production delivery.
Hydraulic fracturing operations often involve the use of a wide range of chemical components and the industry has understood for some time that chemical reactions take place both during and after fracture treatments have been performed. Post fracture treatment a wide range of differing chemical effects can take place and this may continue for some time during the extensive flowback and clean-up period. Such chemistries can result in a range of differing effects, including unplanned scaling tendencies, corrosional behaviour and can even influence aspects such as hydrate control. Such effects can also have an adverse impact on the well itself, the surface manifolding/valves, gathering system and production facilities and need to be well appreciated in order to remove issues.
During the early Appraisal of the Barik formation, in Block 61 in the Sultanate of Oman, H2S had been observed during the post-frac well-test operations. However, the Barik reservoir within the Khazzan field, was believed to be sweet and not reflect a measurable H2S; a characteristic that had been confirmed by performing pre-frac openhole sampling. As had been determined with fracturing operations elsewhere, it was surmised that the frac operations themselves where the potential source of the H2S. Potential causes for this included thermal decomposition of fluid chemistry as well as inadvertent contamination of original source water used for the feed fluid. It had been observed/measured, that the magnitude of H2S reduced with time and was directly related to fracturing fluid clean-up. After extensive investigation the evidence suggested that the root-cause was a combination of the presence of a hardy Sulphate Reducing Bacteria (SRB) species along with the presence of a thiosuplhate feedstock in the frac fluid.
This paper will present a full, robust and coherent analysis of the presence of H2S, the rigorous steps that were followed to identify the root-causes and the identification of potential sources/causes. The paper will present the preventive measures that have been taken and their impact on the overall temporary levels of H2S that have been seen in the operations since. The paper will go on to recommend that for future operations, particularly start-up areas, as transitory levels of H2S might not be identified, not because H2S is not there but rather that there is typically no apparatus nor sufficiently accurate surveillance in place on everyday operations to precisely identify such material.
|File Size||1 MB||Number of Pages||15|
Al Shueili, A.M., Al Manji A. and Rylance, M. 2016 Khazzan: Making the Most of the Fracturing Sweet-Spot Between Verticals and Horizontals. SPE HFTC, The Woodlands, Houston, TX, USA 9-11 February. SPE-179140-MS, http://dx.doi.org/10.2118/179140-MS
Clark, R.A., Al-Busafi, B.S., Imtiaz, A., Al-Lawati, H.M., Huggins, P. and Rainey, S. 2011 A Comprehensive Approach to Surveillance in Appraisal of a Tight Gas Project in Central Oman. SPE MEUG Conf. and Exh., Muscat, Oman, 31-January – 2 February. SPE-142754-MS http://dx.doi.org/10.2118/142754-MS
Clark, R. A., Husain, A., and Rainey, S. 2015 Successful Post-Fracture Stimulation Well Cleanup and Testing of Tight Gas Reservoirs in the Sultanate of Oman. SPE MEUG Conf. and Exh., Muscat, Oman, 26-28 January, SPE-172957-MS, http://dx.doi.org/10.2118/172957-MS
Dolla, A., Fournier, M. and Dermoun, Z. 2006 Oxygen defense in sulfate-reducing bacteria, Journal of Biotechnology 126 (2006) 87–100 http://dx.doi.org/10.1016/j.jbiotec.2006.03.041
Natusch, D.F.S., Sewell, J.R. and Tanner, R.L., 1974, Determination of Hydrogen Sulphide in Air: An Assessment of Impregnated Paper Tape Methods, United States: N. p., 1974. http://dx.doi.org/10.1021/ac60339a001
Ogunsanya, T., & Li, L. 2018 Safe Boundaries of High-Temperature Fracturing Fluids. SPE Western Regional Meeting, Garden Grove, CA, USA, 22-27 April. SPE-190029-MS http://dx.doi.org/10.2118/190029-MS
Rylance, M., Judd, T. C. and Makmun, A. 2011 After Closure Analysis an Underutilized and Undervalued Approach to Understanding kh. SPE MEUG Conf. and Exh., Muscat, Oman, 31-January – 2 February. SPE-141681-MS http://dx.doi.org/10.2118/141681-MS
Rylance, M., Nicolaysen, A., Judd, T.C., Ishteiwy, O.A., Huey, T. and Giffin, W.J. 2011 Hydraulic Fracturing : Key to Effective Khazzan-Makarem Tight Gas Appraisal. SPE MEUG Conf. and Exh., Muscat, Oman, 31-January – 2 February. SPE-142783-MS http://dx.doi.org/10.2118/142783-MS
Structhemeyer, C.G., Morrison, M.D. and Elshahed, M. A 2012 Critical Assessment of the Efficacy of Biocides Used During the Hydraulic Fracturing Process in Shale Natural Gas Wells. International Biodeterioration & Biodegradation 71:15-21 http://dx.doi.org/10.1016/j.ibiod.2012.01.013