Evaluation of Ilmenite as a Weighting Material in Oil-based Drilling Fluids for HPHT Applications
- J. Xiao (Texas A&M University) | H. A. Nasr-El-Din (Texas A&M University) | M. Al-Bagoury (Elkem Materials Ltd.)
- Document ID
- Society of Petroleum Engineers
- SPE European Formation Damage Conference & Exhibition, 5-7 June, Noordwijk, The Netherlands
- Publication Date
- Document Type
- Conference Paper
- 2013, Society of Petroleum Engineers
- 2.7.1 Completion Fluids, 1.10 Drilling Equipment, 2.2.3 Fluid Loss Control, 1.11 Drilling Fluids and Materials, 1.8 Formation Damage, 2 Well Completion, 1.6 Drilling Operations, 6.2.4 Industrial Hygiene, 1.6.9 Coring, Fishing
- oil based, HPHT, ilmenite, weighting material
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Ilmenite (FeTiO3) with a mean particle size of 30 - 45 µm was first introduced into the oil industry as weighting material in 1976. However, its use was limited mainly because of its abrasiveness to drilling equipment. Recently, a superfine ilmenite (5 µm) was introduced to address shortcomings of the traditional weighting materials. The objective of this study is to discuss the performance of oil-based drilling fluids using ilmenite as a weighting material for HPHT applications.
Oil-based drilling fluids with a density of 1.92 SG containing API standard barite and ilmenite were compared. HPHT filtration tests under static and dynamic conditions were conducted at 300°F and 300 psi. Indiana limestone cores with an average porosity of 23 vol% and an average permeability of 100 md were used in the filtration tests. The rheological properties, sag tendency, the volume of filtrate, and the filter cake thickness of the oil-based drilling fluids were determined before and after heating at 400°F for 16 hours.
Results showed that ilmenite-based drilling fluids had a sag factor of < 0.3 and a plastic viscosity of 25-30 cp, much lower than those of barite. HTHP filtration tests showed that under static conditions, the filter cake had a thickness of 0.18 in. and 2.9 cm3 of filtrate volume; while under dynamic conditions, the filter cake thickness was 0.15 in. and the filtrate volume was 2.2 cm3. The rheological properties of oil-based drilling fluids were constant after heating at 400°F for 16 hours. The filter cake thickness and sag factor were small even after 16 hours of heating. This study provides an evaluation of oil-based drilling fluids with ilmenite as a weighting material for HPHT wells, and gives recommendations on how to use it in the field.
Weighting materials are additives used to adjust the density of drilling fluids. The choice of weighting agent to be used in drilling fluids is determined by many factors. One of the most important factors is to provide low rheology in high density fluids and low sag (Zamora and Bell 2004; Zamora 2007).
API standard barite is by far the most commonly used weighting agent in drilling fluids. However, it is not suitable for all drilling fluids applications. One of the major disadvantages of barite is sag (the tendency to settle upon aging) and high rheology (plastic viscosity) particularly in high density drilling fluids (Aldea et al. 2001; Meeten 2001). Another disadvantage is the low hardness (2.5-3.5), which can, on prolonged shearing, lead to the creation of fine colloidal particles that contribute to increasing the gel strength of the drilling fluids and may cause formation damage (Guo et al. 2012). Barite cannot be used in formate brine as it dissolves. Barite is very difficult to remove from the reservoir except by using expensive chelating agents to dissolve it and remove any formation damage (Bern et al. 2010).
However, there are specialized weighting agents such as manganese tetroxide (Mn3O4) or treated micronized BaSO4 with an average particle size of 1 µm. These can provide high density fluids with low sag, low rheology and are less damaging to the formation. Mn3O4 is used in both drilling and completion fluids when low sag, low rheology and ECD (equivalent circulating density) management are required (Svendsen et al. 1995).
Ilmenite (FeTiO3) with a mean particle size of 30 - 45 µm was first introduced into the oil industry as a weighting material in 1976 (Haaland et al. 1976; Fjogstad et al. 2000; Saasen et al. 2001; Blomberg and Melberg 1984). However, its use was limited mainly because of its abrasiveness to drilling equipment. Abrasiveness was solved by removing the coarse particles from the ilmenite. There were magnetic issues, which were solved by reducing the magnetite content. A number of different particle size distributions have been tested since 1993. Recently, a superfine ilmenite (5 µm) was introduced to address shortcomings of the traditional weighting materials (Al-Bagoury and Steele 2012).
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