Design Of JJ158-33-T Derrick

With the large-scale exploration and development of offshore oil fields,the number of wells is increased.Most of the old wells after long-term exploration need regular maintenance to produce oil,which is an important measure to improve oil well utilization and crude oil recovery.Comparing to working in land,there exist large difference in the drilling and maintenance works in the ocean due to the harsh sea climate.In the design of the ocean workover rig should consider the influences of wind load and corrosion except the factors in the design of the onshore workover rig.The derrick is a special steel structure,which is primarily responsible for the various loads generated in the drilling process.The derrick is designed and calculated to ensure that the load can be safely and reliably supported within the stipulated time.The load of derrick is uncertain.The parameters of design related to the load are generally determined according to the relevant standards or norms,but they would be appropriately adjusted in the specific work environment.The type of failure of the derrick structure depends primarily on the type of load and structure,and it is also related to the calculation of the control design.Derrick usually has a variety of different types of damage,such as component or bar parts of the local damage,the destruction of the overall structure.Therefore,the calculation of design not only needs to consider different calculation requirements,but also selects the different calculation methods based on the different use requirements.The design idea for improving product reliability in derrick of current marine workover rig is generally adopted by increasing the safety factor and other measures,then resulting in the size and weight of workover rig are too large,so the cost of the product and transportation,installation,commissioning costs increased.With the increasingly fierce competition in oil equipment and the falling price of international oil,using new methods for the design of derricks have an important and far-reaching significance on oil equipment manufacturing enterprises.In this paper,the technical parameters of the offshore oil 16-2 platform and the characteristics of the drill floor structure were combined,targeted to design on the modularized layout of the JJ158/33-T derrick is proposed following.This work optimizes the derrick of the domestic workover rig by using the modern design method.In the analysis and calculation,the probability of occurrence of various loads in the derrick under different working conditions is taken into consideration.According to the most unfavorable situation of the structural action,the load was combined reasonably for analysis and calculation.Based on the SACS finite element model,the strength of the derrick in the static stateand different working conditions is calculated with a model.The strength meets the requirements of different conditions.In the design of modular derrick of ocean workover rig,the technical specifications of oil workover rig(SY/ T5202-2004)and API related standards are followed.The structure of the derrick includes the form of the elevation and the layout of the web.The shape of the derrick depends mainly on the working conditions of the derrick and the manufacturing process.There are two common kinds of shape: trapezoidal and rectangular.Trapezoidal shape was used in the tower derrick,rectangular shape was used in the A-type derrick and K-type derrick.Since the upside size of trapezoidal was small and downside size was big,as well as good stability,strong carrying capacity,the derrick is often used trapezoidal shape.K-type derrick and A-type derrick need to use the rig's own power from the ground,both of which are at the bottom with the pin and the base connected together.When derrick was put down,the derrick body should be rotated around the bottom pin 90 degrees,If the trapezoid was used on the side,the structure is difficult to deal with.So the rectangular was used in the side,rectangular processing is convenient,when bar end was fixed,the structure was in good stability.As the front does not need to rotate,the trapezoidal was used to improve the carrying capacity.The calculation of wind load in modular lifting section of derrick hoisting should meet the API Spec 4F specification and the hoisting segment of derrick was calculated.The three-dimensional model of each derrick section is established by SACS 5.7 design software.The loads were designed on the basic of the wind speed(28m/s)provided by party A and the requirements of working condition,then segments of derrick have carried on the finite element calculation.According to the results of finite element calculation and theoretical analysis,the safety factor of each derrick is presented following the corresponding terms of API Spec 4F and indexes of design material.