Novel Water Based Mud for Shale Gas Part II: Mud Formulation and Performance
- Meghan Riley (M-I Swaco) | Emanuel Stamatakis (M-I Swaco) | Katherine Price (M-I Swaco) | Steven Young (M-I Swaco) | Guido De Stefano (M-I Swaco)
- Document ID
- Society of Petroleum Engineers
- SPE/EAGE European Unconventional Resources Conference and Exhibition, 20-22 March, Vienna, Austria
- Publication Date
- Document Type
- Conference Paper
- 2012. Society of Petroleum Engineers
- 7.4.3 Market analysis /supply and demand forecasting/pricing, 4.1.2 Separation and Treating, 1.11.2 Drilling Fluid Selection and Formulation (Chemistry, Properties), 1.11 Drilling Fluids and Materials, 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 5.8.2 Shale Gas, 2.7.1 Completion Fluids, 2 Well Completion, 4.6 Natural Gas, 1.6.6 Directional Drilling, 5.1.1 Exploration, Development, Structural Geology, 1.6 Drilling Operations, 4.1.5 Processing Equipment
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Shale-gas plays and other unconventional resources have gained significant importance worldwide. Historically, synthetic based drilling fluids (SBM) are used in these plays when no environmental concerns are in place and are preferred when wellbore stability is necessary. In this paper, we study the use of an improved water based drilling fluid (WBM) that is simple in formulation and maintenance that shows excellent rheological properties, maintains wellbore stability, and a good environmental profile. A combination of well-known and economically affordable materials is combined with new technology to achieve desired rheological properties and wellbore stability.
The use of nanoparticles to decrease shale permeability by physically plugging nanoscale pores holds the potential to remove a major hurdle in confidently applying water-based drilling fluids in shale formations, adding a new advantage to the studied fluid. Silica nanomaterials were investigated for this purpose. Due to their commercial availability, these materials can be engineered to meet the specifications of the formation. Characterization of the nanoparticles was completed with Transmission Electron Microscopy (TEM), dynamic light scattering, and X-ray-photoelectron spectroscopy. Rheological properties and fluid
loss are studied together with other important properties such as shale stability and anti-accretion properties. The authors will describe new laboratory methods used to investigate these properties, from a modified API fluid loss test to the Shale Membrane Test that measures both fluid loss and plugging effects and illustrate additional future research that includes adding reactive species, and anchoring them to the pores, thus stabilizing the shale further.
Natural gas plays a very important role in the U.S. energy demand. The development of gas plays, such as the Barnett or Marcellus, has been triggered by rising energy prices as a result of depleting conventional fields around the world, the need to find a local source of energy and lower the dependency on foreign oil, and is becoming increasingly important. Shale gas is a natural gas produced from shale formations that typically act as both a reservoir and source rock for the natural gas. Geologically, it is a sedimentary rock that is composed mostly of clay-sized particles. The very fine, sheet-like formation causes several wellbore stability issues during the drilling operation. When drilling in overbalanced conditions, mud pressure will penetrate progressively into the formation; due to a combination of saturation and low permeability, only a small volume of filtrate penetrates into the wellbore. This leads to an increase in pore fluid pressure near the wellbore and consequently, a less stable wellbore condition is created. This is especially important in horizontal drilling, which is largely used because of the ability to drain shale gas resources from a geographical area that is much larger than a vertical well due to the exposure of the targeted formation and reduces the traffic within the field. Generally, Synthetic Based Muds (SBM) are the preferred systems used in these regions due to the higher stability in the formation and the higher lubricity during horizontal drilling.
Shale stability when using a Water Base System (WBS) can be achieved by minimizing the mud pressure penetration on the wellbore or physically plugging the formation. Commercially available fluid loss agents are not able to form a filter cake due to low level of fluid movement into the shales and therefore cannot stop the intrusion of fluid or water. Combinations of such technologies with nanosized inert materials seem to achieve the goal quite successfully.
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