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Liu W.,China University of Petroleum - Beijing | Zhang H.,China University of Petroleum - Beijing | Lu B.,China Great Wall Drilling Engineering Co. | Li S.,China Great Wall Drilling Engineering Co.
Natural Gas Industry | Year: 2014

An overseas oil and gas project often involves complicated international political situation, adverse natural environment, cross-cultural differences, and social security, etc. so a higher requirement will be needed for overseas operation safety management. In this case, an enterprise's safety culture is of realistic significance to the guarantee of a smooth overseas operation. Collecting many experiences from different overseas projects, the CNPC Great Wall Drilling Engineering Co., Ltd. has learned advanced management methodologies, adopted modern safety measures, improved safety management level, and adopted unique countermeasures to meet all sorts of challenges, which is all summarized as follows. First, such concepts as felt leadership, localization management, straightline management responsibilities are realized. Second, personnel localization strategy and safety cultural fusion are practiced. Third, emergency management is focused on and local employee's initiative is given full play in it. Fourth, all training programs are practical and targeted. Fifth, the HSE management system is an integral and essential part of the project's special management. Sixth, the policy execution is highly improved. With the above countermeasures, this company has made great success in many overseas projects: safety management concepts have been rooted in the staff member; employees' consciousness and execution are both significantly enhanced; and the security incidents rate is decreasing each year. As a result, the CNPC Great Wall Drilling has become a well-known company providing customer-satisfying oil and gas drilling service all over the world and been widely recognized by international counterparts. This will provide reference for overseas projects operated by other companies.


Liu N.,China Great Wall Drilling Engineering Co. | Liu M.,China Great Wall Drilling Engineering Co. | Liu M.,China University of Petroleum - Beijing | Zhang S.,China University of Petroleum - Beijing
Natural Gas Industry | Year: 2015

Shale gas reservoirs generally need to be fractured to reach the industrial production. However, the flowback ratio of fractured shale gas wells is low. In view of this, the effects of natural fracture spacing, fracture conductivity, fracturing scale, pressure coefficient and shut-in time on the flowback ratio were examined by a joint method of numerical simulation and experiments, and the causes of flowback difficulty of shale gas wells were analyzed. The results show that the flowback ratio increases with the increase of natural fracture spacing, fracture conductivity and pressure coefficient and decreases with the increase of fracturing scale and shut-in time. From the perspective of microscopic mechanism, when water enters the micro-crack of the matrix through the capillary self-absorbing effect, the hydrogen bonds between the particles are replaced by the hydroxyl group, namely, hydration effect, giving rise to the growth of new micro-cracks and the propagation of the main fractures, and complex fracture networks are generated, so a large proportion of water cannot be flowed back, resulting in a low flowback ratio. In shale gas well fracturing, generally there is small fracture space, fracture conductivity and big fracturing volume, so a large proportion of the injected water will be held in the very complex fracture network with a big specific area, and is unable to flow back. It is concluded that the flowback ratio of fractured shale gas wells is affected by several factors, but deliberately seeking to a high flowback ratio is not necessary, because low flowback shale gas wells, instead, usually have high production. ©, 2015, Natural Gas Industry Journal Agency. All right reserved.

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