Crane Barge Research Articles

大水深海域における海洋石油開発システムの変遷について

Offshore oil and gas development activities began after World War II. For several decades jacket type production systems were widely used for shallow water oil and gas projects. In 1970s floating type systems (semi-sub and FPSO) appeared in deeper waters where the fixed type could not be technically or economically installed. The deepwater age began in the 1990s when technical break-throughs were realized in the floater design, mooring design, large crane barge capacity and subsea completion technology as their engineering and analytical capabilities had advanced. At present, those technologies enable us to drill in water depth of more than 3,000m and to produce hydrocarbons in water depth of 2,300m.We may envisage soon that crude will be recovered from under 3,000m water depths if high oil prices continue, especially in the Gulf of Mexico and/or offshore Brazil where advanced offshore technology has been created by industry. There are still some hurdles to overcome, such as floater capability expansion, subsea boosting and processing reliability enhancement, flow assurance and remotely operated vehicle (ROV) technology.

An Aid to Operating Decisions Based on Nonlinear Response of a Crane Barge in Waves

A nine-degree-of-freedom time domain mathematical model was used to numerically simulate crane ship dynamics. This model considers the elasticity and damping of the hoisting rope assembly and includes arbitrary, biangular swing of the suspended hook load coupled with surge, sway, heave, roll, pitch, and yaw motions of the hull. The linear frequency-dependent hydrodynamic response to the hull’s own motions accounted for memory effects that were approximated in the time domain by a finite state space model. The nonlinear hydrodynamic drag force acting on the oscillating hull was quadratically approximated using an empirical drag coefficient. The incident wave force on the hull consisted of the first-order force oscillating at wave frequency and the second-order slowly varying wave drift force. The nonlinear horizontal mooring system restoring force was approximated by a third-order polynomial. To specify operating limits for a shear-leg crane barge in a heavy lift offshore operation, a stochastic analysis was performed based on the system’s simulated dynamic response in an ensemble of natural seaways.

Response Analysis and Operating Limits of Crane Ships

Results are presented of a recent research project with the objective of quantitatively predicting the dynamic response of crane ships during lifting operations offshore. For this purpose, a mathematical simulation model was developed. This model considers the elasticity and damping of the hoisting rope assembly and includes bi-angular swing of the hook load coupled with hull motions. The nonlinear, time-domain motion equations comprise effects of gravity, buoyancy, hydrodynamic reactions, viscous drag, wave excitation, and the mooring system. The mathematical model was verified by comparing calculated system response with corresponding measurements from scale-model tests. To derive transfer functions of system response, the dynamic motion equations were linearized about the system's equilibrium state. The dynamic behavior of a shear-leg crane barge and a semisubmersible crane vessel was investigated and operational limits were specified. Based on these limits, obtaining the crane ships' probability of successfully performing a heavy lift was demonstrated.

Full scale offshore pile tests in calcareous sands : de Andrade Martins, J C Proc 10th International Conference on Offshore Mechanics and Arctic Engineering, Stavanger, 23–28 June 1991V1-Part B, P611–615. Publ New York: ASME, 1991

The objectives were to measure engineering properties of local calcareous sand and to verify the feasibility of four non conventional offshore piled foundation. Full scale pile tests were conducted in 86 m water deep, first from semi-submersible drill rig and from a crane barge. Static pull out tests at three specific layers shown skin friction according literature, except strongly cemented deeper layer. Dynamic pile driving monitoring was used and closed end pile driving monitoring was used and closed end pile proved feasibility, reducing length compared with open end piles, satisfying design and economics considerations. Finally it's recommended to use template installation as a geotechnical testing to minimise design uncertainty and reducing costs without loss of safety, specially in calcareous soils.

A new methodology developed by cetena to assess the seakeeping behaviour of marine vessels

The paper describes an analytical method to determine an operability index for a marine vehicle when its geometric characteristics, the geographical area in which the vessel is supposed to operate, and the limiting criteria for operations are known. The computer program based on strip theory provides reliable results not only for conventional hullforms, but also for catamarans, offshore vehicles, etc. The results are presented in the form of figures for different vessels, namely, crane barge, naval vessels and SWATH type catamarans. The authors are of the opinion that the proposed method would provide the designer with a valid tool to improve the seakeeping qualities of a vessel, while taking into account the limiting conditions imposed due to seaway operations.

Forces in the hoisting wire of a crane barge in waves

In this report a description is given of a method by which the influence can be determined of the dynamic motions of a derrick barge and of the object to be hoisted on the forces in the hoisting wire. The results of these calculations are used for an optimization study in which several parameters of the hoisting system have been varied. It is also shown that the results of these preparatory calculations can be used for establishing the maximum sea conditions in which hoisting operations can still be executed without the maximum allowable stress in the hoisting wire being exceeded.

A System for Tieback of Subsea Wells to Fixed Platforms

Summary Tieback systems allow wells drilled with floating drilling vessels and subsea drilling equipment to be tied back later to a platform installed over the subsea wells. The system includes templates and equipment for drilling, platform location and guidance, and tieback. Introduction Over the past few years, a different approach to developing offshore oil fields with platforms has proved to be economical, practical, and reliable. This approach allows development drilling and platform construction to occur concurrently. First, a subsea template is installed. The desired number of wells is drilled through the template using a floating vessel, while the platform is constructed at a separate location. The drilling vessel is moved, and the fixed platform is installed over the subsea template. Then, the subsea wells can be tied back to the platform deck. The tubing is run, surface production trees are installed, and the wells are produced in the conventional manner (Fig. 1). This method provides quicker production from an offshore field, with resulting accelerated return on the investment.Several of these tieback systems currently are producing to platforms, and numerous other offshore operators have installed templates and presently are drilling subsea wells through these templates.This paper describes the equipment used with this system for providing early production of oil fields as well as the experience gained to date. The equipment includes subsea templates, subsea drilling equipment, platform location and guidance equipment, and tieback equipment. Subsea Templates The subsea template (1) provides the base through which the subsea wells are drilled and (2) spaces and aligns the subsea wellhead equipment. Three basic types of subsea templates are unitized, modular, and spacer. Each template type has advantages in a particular application.The unitized template (Fig. 2) is recommended for water depths greater than 300 ft (90 m) and for use with more than six wells. Fabricated from 30-in. (762-mm) or larger tubular members, it incorporates receptacles for each well and for a three- or four-point leveling system. It normally will include receptacles for the installation of the platform location and guidance equipment.The template is fabricated at a dockside facility, Depending on the desired method of installation, the template either will be fabricated as a "passive" template or will incorporate built-in buoyancy control. After nondestructive and functional testing, the template is transported by barge to the drilling location. The unitized template is lowered to the ocean floor using one of the following methods.The passive unitized template simply is lowered to the ocean floor by a crane barge. The crane barge lifts the template from the work barge. Once it is in the water, the template load is transferred to lines connected to one or more deck winches for lowering to the ocean floor.Another method of installation requires incorporation of provisions for controlled buoyancy in the template. Such a template is initially buoyant. The cargo barge is submerged partially, and the template is floated off. Lines are attached from the template to the drawworks of a drilling vessel. As the template is ballasted, a work boat assists in keelhauling the template under the drilling vessel. JPT P. 188^