Browsing by Subject "proppant"
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Item Fracture Conductivity of the Eagle Ford Shale(2014-07-25) Guzek, James JHydraulic fracturing is a well completions technique that induces a network of flow channels in a reservoir. These channels are characterized by fracture conductivity, a measure of how easily a liquid or gas flows through the fracture. Fracture conductivity is influenced by several variables including fracture surface roughness, fracture closure stress, proppant size, and proppant concentration. The proppant concentration within a fracture can significantly affect the magnitude of fracture conductivity, which enhances the productivity of a hydraulically fractured well. Therefore, understanding the relationship between proppant concentration and fracture conductivity is critical to the successful development of unconventional reservoirs such as the Eagle Ford Shale. This work investigates the fracture conductivities of seven Eagle Ford Shale samples collected from an outcrop of facies B. Rough fractures were induced in the samples and laboratory experiments that closely followed the API RP-61 procedure were conducted on the samples to measure the unpropped and propped conductivities. Propped experiments were performed with 30/50 mesh white sand at two different areal concentrations within the fracture, 0.1 lb/ft^(2) and 0.2 lb/ft^(2). Assuming a cubical packing arrangement, the proppant pack is calculated to be a partial monolayer of 0.8 layers at 0.1 lb/ft^(2) and a pack of 1.6 layers at 0.2 lb/ft^(2). The results show that when the fractures are propped with 0.1 lb/ft^(2) or 0.2 lb/ft^(2), fracture conductivity values are approximately two orders of magnitude greater than unpropped conductivity values. Therefore, even low areal concentrations of proppant in a fracture can significantly enhance conductivity in the Eagle Ford Shale. Comparing the results of the two propped experiment types, conductivity values at 0.1 lb/ft^(2) proppant concentration are on average 49% higher than conductivity values at 0.2 lb/ft^(2). This difference is attributed to the partial monolayer pack at 0.1 lb/ft^(2) and proppant pack of 1.6 layers at 0.2 lb/ft^(2). However as closure stress increases from 1,000 psi to 6,000 psi, fracture conductivity at 0.2 lb/ft^(2) decreases more slowly than conductivity at 0.1 lb/ft^(2). These results suggest that the conductivity of the denser proppant pack at 0.2 lb/ft^(2) is more resistant to the flow inhibiting effects caused by proppant embedment and proppant crushing.Item The Effect of Proppant Size and Concentration on Hydraulic Fracture Conductivity in Shale Reservoirs(2013-04-11) Kamenov, AntonHydraulic fracture conductivity in ultra-low permeability shale reservoirs is directly related to well productivity. The main goal of hydraulic fracturing in shale formations is to create a network of conductive pathways in the rock which increase the surface area of the formation that is connected to the wellbore. These highly conductive fractures significantly increase the production rates of petroleum fluids. During the process of hydraulic fracturing proppant is pumped and distributed in the fractures to keep them open after closure. Economic considerations have driven the industry to find ways to determine the optimal type, size and concentration of proppant that would enhance fracture conductivity and improve well performance. Therefore, direct laboratory conductivity measurements using real shale samples under realistic experimental conditions are needed for reliable hydraulic fracturing design optimization. A series of laboratory experiments was conducted to measure the conductivity of propped and unpropped fractures of Barnett shale using a modified API conductivity cell at room temperature for both natural fractures and induced fractures. The induced fractures were artificially created along the bedding plane to account for the effect of fracture face roughness on conductivity. The cementing material present on the surface of the natural fractures was preserved only for the initial unpropped conductivity tests. Natural proppants of difference sizes were manually placed and evenly distributed along the fracture face. The effect of proppant monolayer was also studied.Item The Influence of Vertical Location on Hydraulic Fracture Conductivity in the Fayetteville Shale(2014-05-05) Briggs, KathrynHydraulic fracturing is the primary stimulation method within low permeability reservoirs, in particular shale reservoirs. Hydraulic fracturing provides a means for making shale reservoirs commercially viable by inducing and propping fracture networks allowing gas flow to the wellbore. Without a propping agent, the created fracture channels would close due to the in-situ stress and defeat the purpose of creating induced fractures. The fracture network conductivity is directly related to the well productivity; therefore, the oil and gas industry is currently trying to better understand what impacts fracture conductivity. Shale is a broad term for a fine-grained, detrital rock, composed of silts and clays, which often suggest laminar, fissile structure. This work investigates the difference between two vertical zones in the Fayetteville shale, the FL2 and FL3, by measuring laboratory fracture conductivity along an artificially induced, rough, aligned fracture. Unpropped and low concentration 30/70 mesh proppant experiments were run on samples from both zones. Parameters that were controllable, such as proppant size, concentration and type, were kept consistent between the two zones. In addition to comparing experimental fracture conductivity results, mineral composition, thin sections, and surface roughness scans were evaluated to distinguish differences between the two zones rock properties. To further identify differences between the two zones, 90-day production data was analyzed. The FL2 consistently recorded higher conductivity values than the FL3 at closure stress up to 3,000 psi. The mineral composition analysis of the FL2 and FL3 samples concluded that although the zones had similar clay content, the FL2 contained more quartz and the FL3 contained more carbonate. Additionally, the FL2 samples were less fissile and had larger surface fragments created along the fracture surface; whereas the FL3 samples had flaky, brittle surface fragments. The FL2 had higher conductivity values at closure stresses up to 3,000 psi due to the rearrangement of bulky surface fragments and larger void spaces created when fragments were removed from the fracture surface. The conductivity difference between the zones decreases by 25% when low concentration, 0.03 lb/ft^(2), 30/70 mesh proppant is placed evenly on the fracture surface. The conductivity difference decrease is less drastic, changing only 7%, when increase the proppant concentration to 0.1 lb/ft^(2) 30/70 mesh proppant. In conclusion, size and brittleness of surface fracture particles significantly impacts the unpropped and low concentration fracture conductivity.