No abstract

An environmentally friendly and highly efficient electrochemical method has been developed for halogenation of 2H‐indazoles with cheap and commercially available NaX (X=Cl, Br) in the absence of metal catalysts and oxidants. Notably, this electrochemical process exhibits a broad substrate scope and high functional‐group compatibility. A variety of 2H‐indazoles are compatible with this transformation to give the corresponding products in modern to excellent yields. Also, this practical protocol avoids using external expensive supporting electrolytes. Last but not least, the procedure was carried out in an undivided cell at constant current condition under air atmosphere.

With the development of Chang Qing Oilfield, the following technical problems are faced: the increasing proportion of the low-production and low-efficiency wells, the worse production of pertinence and effectiveness in conventional retreatments and a large amount of remaining oil between wells and layers. In this case, the technique of radial fracture network fracturing and deep plugging has been proposed. Meanwhile, the matching products which include variable viscosity diverting acid, micro expansion high strength plugging agent and temporary plugging agent (oil soluble, water soluble and anti-scale) have been developed as well. Nowadays, the retreatment technology has been successfully tested and popularized in Chang Qing oilfield. Compared with the conventional retreatments, these two technologies have remarkable effect on increasing production and prospective application.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe essence of fracture reorientation of refracturing is rock failures. Therefore, the study on reorientation mechanism should be started from studying rock failures, taking the influences of objective and subjective factors such as reservoir microfracture distribution, geostress field, rock mechanics characteristics, physical properties and the methods of wellcompletion, injection/production, hydraulic fracturing technology upon fracture reorientation into account. As a result, the conditions that rock failures occur were analyzed, thus the theory criteria for fracture reorientation was given, namely the critical bottomhole pressure required and the conditions which the geostress field and rock mechanics parameters should have. The new fractures are divided into shear fractures and tensile fractures, which correspond respectively to the two kinds of rock basic failure mechanisms-shear failure and tensile failure. The azimuths of these two kinds of fractures are both different from the initial hydraulic fracture (abbr.IHF), and the critical pressure is the function of the geostress field and rock mechanics parameters. Based on the above criteria, utilizing the refracturing data of Chang 6 formation, the feasibility of fracture reorientation for Wangyao section was investigated. And three typical wells were analyzed in details, which show the refracture characteristics we predict accord with that of microseismic monitoring or the curve of the treating pressure. It indicates that even if the geostress field keeps unchanged, fracture reorientations can be achieved by other ways. In the certain range of parameters for reservoir physical properties, if a proper fracturing technology, such as TSO (i.e. Tip Screen Out) with temporarily blocking treatment (abbr.TBT), can be applied so as to create the treating conditions that meet the demand of the above criteria, the refracturing can produce new fractures in Wangyao. And for refracturing treatments, with the shot holes along the IHF azimuth blocked effectively, multi-fractures and new fractures can be achieved by oriented perforations.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe essence of fracture reorientation of refracturing is rock failures. Therefore, the study on reorientation mechanism should be started from studying rock failures, taking the influences of objective and subjective factors such as reservoir microfracture distribution, geostress field, rock mechanics characteristics, physical properties and the methods of wellcompletion, injection/production, hydraulic fracturing technology upon fracture reorientation into account. As a result, the conditions that rock failures occur were analyzed, thus the theory criteria for fracture reorientation was given, namely the critical bottomhole pressure required and the conditions which the geostress field and rock mechanics parameters should have. The new fractures are divided into shear fractures and tensile fractures, which correspond respectively to the two kinds of rock basic failure mechanisms-shear failure and tensile failure. The azimuths of these two kinds of fractures are both different from the initial hydraulic fracture (abbr.IHF), and the critical pressure is the function of the geostress field and rock mechanics parameters. Based on the above criteria, utilizing the refracturing data of Chang 6 formation, the feasibility of fracture reorientation for Wangyao section was investigated. And three typical wells were analyzed in details, which show the refracture characteristics we predict accord with that of microseismic monitoring or the curve of the treating pressure. It indicates that even if the geostress field keeps unchanged, fracture reorientations can be achieved by other ways. In the certain range of parameters for reservoir physical properties, if a proper fracturing technology, such as TSO (i.e. Tip Screen Out) with temporarily blocking treatment (abbr.TBT), can be applied so as to create the treating conditions that meet the demand of the above criteria, the refracturing can produce new fractures in Wangyao. And for refracturing treatments, with the shot holes along the IHF azimuth blocked effectively, multi-fractures and new fractures can be achieved by oriented perforations.