RESEARCH OF MAIN CHARACTERISTICS OF SEMI-SUBMERSIBLE FLOATING DRILLING RIGS AT THE INITIAL STAGES OF DESIGN
The paper presents a design scheme for estimating the main characteristics of semisubmersible floating drilling rigs at the initial stages of design. According to the analysis results of loading items of the a semisubmersible drilling rig hull, it is evident that all items, except for the mass of the metal hull (technological equipment and stores, main mechanisms, ship supply and fuel), mainly depend on the depth of drilling and can be adopted on the basis of the prototype with a sufficient degree of accuracy at the beginning of design. Relative to the semisubmersible drilling rig type, the volume of ballast received for moving to the working position depends on the height of the freeboard of the pontoons and on the volume of the columns to the waterline of the working position. The ballast chosen in this way should be placed only in the lower pontoons which also have compartments for pumps and fuel tanks. Taking into account buoyancy conditions in the marching and working (semi-submersible) position, as well as requirements specification for the design of semi-submersible floating drilling rigs, there have been found dependencies which allow obtaining and analyzing characteristics of the pontoons and columns, as well as the rig’s heaving parameters required at the starting stage of design. To determine the size and volume of the hull (pontoons, stabilizing columns and upper hull), there has been proposed an order for calculating the characteristics of semi-submersible floating drilling rigs. The estimation of the rig’s heaving motions when drilling occurs in the rough sea has been done. The technique obtained can be used in the educational process when studying the design of semisubmersible crafts, such as semisubmersible drilling rigs and floating cranes