Solving Formation Evaluation Challenges in a Potassium Formate Mud Environment - A Kuwait Case Study of Using Neutron Induced Gamma Ray Spectroscopy Data in a Complex Carbonate Reservoir
- Djisan Kho (Schlumberger) | Jim Grau (Schlumberger) | Heyam Ammar (Kuwait Oil Company) | Badruzzaman Khan (Kuwait Oil Company) | Ealian H. Al-Anzi (Kuwait Oil Company) | Mihira Achary (Kuwait Oil Company)
- Document ID
- Society of Petrophysicists and Well-Log Analysts
- Publication Date
- October 2011
- Document Type
- Journal Paper
- 357 - 368
- 2011. Society of Petrophysics and Well Log Analysts
- 2 in the last 30 days
- 136 since 2007
- Show more detail
Potassium formate based mud has gained widespread acceptance over the past decade, as its physical and chemical properties make it an efficient drilling and completion fluid for high-temperature and high-pressure wells. A formate based mud system using manganese tetra-oxide (Mn3O4) as the weighting material was evaluated in a pilot well in Kuwait, replacing the oil base mud that had been traditionally used. The main objectives of the pilot included obtaining higher quality resistivity-based borehole images, retrieving PVT-quality formation fluid samples, and minimizing formation damage.
Formate mud has drilling and completion benefits, such as stable mud density, low equivalent circulation density, low gas solubility, and reduced formation damage. How-ever, log data interpretation in formate mud presents serious challenges because of its unique properties, including high gamma ray radioactivity, low hydrogen index, high density, and high thermal neutron cross section. Efforts have been made by service providers to characterize their logging tools and to compensate for the effects of potassium formate mud. Most of the efforts have focused on improving borehole environmental correction algorithms. However, formation evaluation using these borehole corrected logs have remained difficult, primarily because mud invasion effects on the nuclear logs prevent the use of traditional petrophysical models for porosity determination. The neutron induced gamma ray spectroscopy log is also affected by the mud properties, particularly by the potassium and manganese content. However, their signatures in the gamma ray energy spectrum can be stripped out, leaving the formation elemental yields intact.
A special petrophysical model utilizing neutron induced gamma ray spectroscopy (NIGS) data and conventional open hole logs has been developed. The NIGS data provide direct inputs to solve the mineralogy of the complex carbonate reservoir, hence reducing the uncertainty of the porosity and water saturation computations. The formation evaluation results in this pilot well are found to be comparable to those from nearby wells drilled with conventional oil based mud.
The application of potassium formate mud in future development wells is encouraged, as all of the primary objectives of the pilot project have been achieved and the formation evaluation challenges have been successfully overcome.
|File Size||6 MB||Number of Pages||12|