Exploration for unconventional reservoirs has begun in various countries in the Middle East. Widely recognized as the bastion of conventional crude oil and gas production, the area's exploration for natural resources –– in particular unconventional resources –– is in its infancy. The lack of fresh water may derail some of the exploration and production of unconventional resources in the Middle East. One of the solutions is to use the abundant availability of nearby sea water for fracturing treatments. This paper will discuss the applicability of sea water for fracturing fluids for without the need for separate treatment of the water. Rheological data with synthetic sea water as well as source sea water from Saudi Arabia, identification of any potential precipitation and remediation and compatibility with produced water and proppant pack conductivity data, of applicable fluids to show the effectiveness of the systems to the high temperatures of the reservoirs in the kingdom, 325°F will also be presented. The concept of using seawater as a base fluid is not new. Because of the problems associated with substituting seawater for freshwater in polymer-based fracturing fluids, many operators are apprehensive about using seawater for fracturing. There have been noted attempts to mix polymer-based fluids on the fly with seawater, but treatment results have varied widely. Seawater contains dissolved inorganic salts, adversely affecting hydration and viscosity development of polymer-based fluids. High content of calcium and magnesium in seawater can reduce viscosity. These salts also buffer and strongly influence pH control and may inhibit or deactivate certain gel breakers. To gel effectively, polymer fluids need a specific mixing environment with distinct pH windows. Borate crosslinking normally requires a high pH. Rheology and breaker profiles will be shown that provide the desired properties and regain conductivity to establish the non-damaging clean-up of a properly designed fluid. The technology presented uses chemical chelation of the problem ions in the sea water, resulting in the fracturing fluids with enhanced fluid and proppant pack properties, including thermal stability, retained fracture conductivity, pH buffering capacity, scale inhibition and fluid loss control. Further, the addition of the novel additives to the fluid does not interfere with the crosslink delay time and does not complicate the preparation of the fluid. The technology discussed eliminates the need for traditional water treatment and nano-filtration of sea water and associated disposal issues.
In oil and gas wells that are hydraulically fractured, wetting properties of surfaces (formation and proppant) significantly affect hydrocarbon and liquid displacement. During the life of a well, the water saturation of surfaces changes, leading to reduction of relative permeability to oil or gas and consequently affecting production. In order to reverse the formation to a reduced water wet state and improve the movement of hydrocarbons, strong water-wet surfactant is pumped. The surfactant is then adsorbed onto the surfaces reducing the capillary pressure and water saturation within the porous systems. This is, however, not a permanent solution, as the surfactant is washed out over time. A more permanent and robust solution is needed. Nature encompasses many examples of biological systems and surfaces that are permanent and have special wettability and interfacial interaction with fluids. Research and development within the last decade in bio-mimicking nature has been fruitful and led to the development of many new surfaces such as superhydrophobic, ice phobic and low-drag surfaces. In this work we apply some of the knowledge and principles found in nature to modify proppant surfaces (silica sand and ceramic proppant) in order to study how wettability will affect the fluids recovery and their interaction with the solid surfaces. Nanotechnology was used to deposit hydrophobic/oleophobic moieties onto the proppant surfaces, and several surface modifiers were tested. These molecules were covalently bonded to the surfaces. The new surfaces were characterized for wettability and flow to water and oil. A new proppant that show promises for improved stimulation fluids recovery and flow was identified and further developed.
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