Rheological Properties of Invert Emulsion Drilling Fluid under Extreme HPHT Conditions
- John Lee (M-I Swaco) | Arash Shadravan (Texas A&M University) | Steven Young (M-I Swaco)
- Document ID
- Society of Petroleum Engineers
- IADC/SPE Drilling Conference and Exhibition, 6-8 March, San Diego, California, USA
- Publication Date
- Document Type
- Conference Paper
- 2012. IADC/SPE Drilling Conference and Exhibition
- 4.1.5 Processing Equipment, 2 Well Completion, 5.8.9 HP/HT reservoirs, 5.2.2 Fluid Modeling, Equations of State, 1.11 Drilling Fluids and Materials, 2.7.1 Completion Fluids, 4.1.2 Separation and Treating, 1.6 Drilling Operations
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Limited amount of rheological data generated under extreme high-pressure, high-temperature, (HPHT) conditions (>500°F/30,000 psi) have been published due to lack of suitable viscometer and drilling fluid for such conditions. This paper compares the rheological properties of invert emulsion drilling fluid generated from four types of HPHT viscometers and provides a simple rheological model that can be used to predict the behavior of OBM under extreme-HPHT conditions.
Previously most of the HPHT studies were limited to 20,000 psi and 500°F. Recently more than one extreme-HPHT rheometers have become commercially available, which can measure the rheological properties of drilling fluids at conditions up to 600°F and 40,000 psi. These viscometers have been used to test various invert emulsion drilling fluid samples to the maximum capacity of the equipment. Parts of the data generated from one particular instrument have been compared with data obtained from other rheometers that are operated at lower temperature and pressure.
The data indicated several factors can critically affect the rheology measurements, including drilling fluid chemistry, instrument set up and test schedule. Rheological properties measured by various instruments differed slightly from each other perhaps due to design differences. Temperature and pressure not only affect the rheological properties of the test fluid but may also impact the performance of the critical mechanical parts used for rheology measurement. In addition, HSE experience gained from working with extreme-HPHT instruments is also included in this paper.
The global growth in hydrocarbon demand is driving oil and gas industry to drill deeper reservoirs. The main challenge in such environments is dealing with the extremes in temperature and pressure. Figure 1 shows the distribution of some HPHT wells located in the US, North Sea, Middle East and South East Asia. The development of HPHT wells has come as an inevitable consequence of the widening of the oil industry's net in a bid to find new reserves as conventional reserves dwindle. Globally, 87 percent of industry players are involved in HPHT assets in some capacity and some 60 percent of these are expecting to put in place an HPHT program within the next two years (Loth 1998, Schlumberger 2011). HPHT operation is defined as wells that have an initial reservoir temperature greater than 300°F and a reservoir pressure greater than 10,000 psi (69 Mpa) or an initial reservoir overpressure greater than 3000 psi (23 Mpa) (Loth 1998). In the current work, the extreme-HPHT condition is used to designate temperature and pressure conditions greater than 500°F, 20,000 psi. Developing HPHT reservoirs with reduced risk requires the understanding of rheological properties of the drilling fluid. Rheological behaviors of oil-based drilling fluids and challenges of HPHT drilling fluids have been previously reported (Houwe and Geehan 1986, Bland et al. 2006).
Invert drilling fluid is often used to drill challenging HPHT wells owing to its inherited thermal stability when compared to water-based drilling fluid. Most of the invert drilling fluids can handle temperatures up to 400°F without significant issues. However, when temperature is above 400°F, the chemicals used in the drilling fluid can become unstable and thermal degradation can occur over a short period of time resulting drastic changes in rheology and other fluid properties. In order to
study the performance of invert drilling fluids under simulated downhole conditions, HPHT viscometers are often used to evaluate the flow properties and thermal stability of test fluids.
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