ABSTRACT
Hydraulic stimulation technique consists of "fracturing" the formation (rock reservoirs) through pumping a fracturing fluid downhole. This operation is performed by using hydraulic fracturing pumps. The pistons of these pumps are mechanical components performing the intake and compressing fracture fluid by reciprocating action. During this alternative cycle, the entry of fine sand in the gap between piston surface and seals causes localized wear of the piston.
Nowadays, commonly used hardening Technology for manufacturing these components is Thermal Spray, which has specific technical weaknesses: chemical and structural inhomogeneity, porosity and lack of adhesion to the substrate due to metallurgical discontinuity between metal base and coating. This paper presents the results obtained by replacing this technique for a new surface treatment using hardening by Plasma Nitriding. The layer obtained has a surface hardness of HV 1100 (Vickers hardness) versus HV 550 achievable with the technique replace, using a DIN 34CrAlNi7 steel as base material.
Proposed treatment is supplemented with a second surface hardening treatment by the technique of PVD: Physical Vapor Deposition, which produces a monolayer coating of Al-Cr-N 5µm thick with a final hardness of HV 2500.
The hardening treatment described, was used to make a series of plungers for hydraulic fracturing, which were tested in a field technological test, supplemented with standardized laboratory tests on specimens that witnessed the manufacturing process. The plungers manufactured using the new technology proposed by YTEC has a durability which is 313% higher than those of Thermal Spray Technology.
Keywords
Hydraulic fractures; pistons; wear; nitriding
