Because natural asphalt has a large molecular weight distribution and a high molecular weight the softening point is high compared to other types of polymers, which allows it to soften or deform as it is nears its softening point instead of completely melting into a low viscosity liquid. Even when natural bitumen is 20 degrees above its softening point, it is still a high viscosity liquid.
From the original source hard natural petroleum, natural bitumen formed with a polymer backbone that is high in functional nitrogen, which gives natural bitumen excellent adhesion and binding properties. It is a natural mineral ore that allows it to be exempt from registration under the European REACH regulations.
The only commercially viable natural bitumen deposits are located in the Kermanshah in west of Iran. The deposits form in vertical veins and families of veins throughout the deposit area. natural bitumen was formed when a unique geologic event caused tension fractures in the rock structure above an existing proto petroleum deposit. This allowed the precursor of natural bitumen to extrude into the cracks in a very pure form. As this material sat in the veins for millions of years, it hardened into the natural bitumen we mine today.
natural bitumen is mined by sinking a shaft into the vein with a series of drifts and slopes extending in opposite directions. Because natural bitumen is a light, friable material we mine it by hand with air operated jackhammers and convey the ore from the mine face to the surface with an airlift.
Since the 1950 we have mined natural bitumen underground, therefore our production is based on the number of miners we have, as well as the number of working faces we have available to send them to. The development of a new mine is complicated, labor intensive, and it takes time; about 9-18 months from the time we start the development of a mine until it is in production.
The main markets we sell natural bitumen into are the oilfield and printing ink industries. In the oilfield, natural bitumen is used as a fluid loss control agent and shale stabilizer for oil based drilling fluids (OBM), and water based drilling fluids (WBM). It is also used as a loss circulation material and slurry density reducer for cementing fluids.
Because of the high softening point and high molecular weight distribution, when natural bitumen is added to the drilling fluid, it acts as a fluid loss control agent and shale stabilizer by partially melting or deforming. This semi-soft material then plugs off micro-fractures in the formation and smears the inside of the well bore to make a tight, tough filter cake. As the drilling fluid continuously circulates, some of the natural bitumen dissolves into the fluid imparting both coating and rheological properties to the fluid. The lubrication from an increase in drilling fluid viscosity and the thin, smooth filter cake sealing off and stabilizing problem formations makes natural bitumen effective in preventing stuck pipe. The main difference between the application of natural bitumen in OBM and WBM is how natural bitumen is added to the drilling fluid system. While it can be added directly in both applications, some people add natural bitumen to a WBM system in a solution with glycol usually referred to as liquid natural bitumen.
In cementing fluids, natural bitumen is used as a lost circulation material (LCM) because of its plugging and binding properties. As it is a light material, it is also used as a slurry density reducer in some specialty cementing fluids.
The adhesion properties of natural bitumen are critical to the application in the printing ink industry. In black publication type printing ink, natural bitumen both disperses the carbon black and acts as a binding agent to hold the carbon black pigment to the paper. This makes for a very crisp image that does not smear or rub off in newspapers and magazines.