1,721,012 research outputs found
Comparative Experimental Study of Rock Cutting under High Confining Pressure and Atmospheric Conditions Using PDC Cutter
No full textImpact of microannulus on the efficiency of heat transfer in the bottomhole
Full text linkTo ensure feasible power generation from closed-loop geothermal wells, deeper wells are required to reach higher temperature zones. However, weak bonding between cement and casing or cement and formation may allow formation of a small gap (known as microannulus), which could have a negative effect on the heat extraction rate and consequently compromises the entire investment. Previous projects have reported that the output temperatures were significantly lower than the expected values, and the cause is believed to be cement debonding. This study aims to develop a reliable simulation model to demonstrate the impact of microannulus in closed-loop geothermal systems. Multi-physics finite element analysis is used to construct models with and without microannulus. The microannulus is modeled based on real cement evaluation logs, with gaps varying between a few micrometers to few millimeters. In extreme cases, the presence of microannulus is found to decrease the geothermal power by more than 35%. Furthermore, the possibility of heat loss containment is investigated by a sensitivity study of wellbore parameters. These sensitivity analyses demonstrate that cement and geothermal fluids with higher thermal conductivity can improve but cannot compensate the presence of microannuli. The results also highlight the importance of proper cementing design to ensure wellbore integrity and avoid geothermal power loss
Using Technology to Avoid Trespass Liability Based on Subsurface Intrusions of Hydraulic Fractures
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Imaging Three-Dimensional Complex Hydraulic Fracture Networks in Horizontal Wells Using Functionally-Graded Electromagnetic Contrasting Proppants
No full textA modified extended finite element method for fluid-driven fractures incorporating variable primary energy loss mechanisms
No full textA Fast Method to Determine the Critical Depth of Cut for Various Rock Types
No full textKnowing correct values of the rock mechanical properties is crucial for many engineering applications in subsurface. Rocks may show two failure modes during cutting: ductile and brittle. In the ductile mode, rock deforms plastically, and the debris is powdered ahead of the cutting face. On the other hand, chips are the major cutting characteristics for the brittle failure during rock cutting. The critical depth of cut represents the transition point between these two models, so knowing this value helps better predict the failure mechanism of rock. In this paper, a new method is introduced based on measuring the roughness of the groove for determining the transition point of failure modes for every rock sample after the scratch test. The graph depicting the average change in the surface roughness (Rt) versus the scratched surface roughness (ΔR) can be used to identify the rock failure mode and determine the transition point for the cutting process. The value of this slope increases until the depth of cut reaches the transition point, and then the slope reaches a constant value. The main purpose of this paper is to estimate the critical depth of cut of different rock specimens employing the new surface roughness model
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