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It gives me great pleasure in presenting this manual on the designing aspects considered in the construction and commissioning of offshore facilities.
This first time effort by the Offshore Design Section has efficiently covered the various design considerations that are essential in constructing offshore facilities. This design manual provides adequate data and references to carry out Basic Engineering of offshore facilities and may serve as a comprehensive guide to any new incumbent in the Offshore Design Section.
The effort put in by the Offshore Design Section in the preparation of this manual is commendable. The Offshore Design Section shall on a regular basis, revise this manual and keep it up-to-date with the designing aspects actually being followed by the Offshore Design Section.
(Mr. I. B. Raina)
(ED – CES)
The Offshore Design Section is a division that provides in-house engineering to the Offshore Works Section in the design and construction of offshore facilities. It has been a constant endeavour of the Offshore Design Section to design minimum-facility offshore platforms in line with International standards and practices, to help exploit the offshore potential of oil and gas at optimum cost. The Offshore Design Section has realized these efforts by constantly reviewing and revising the Design Philosophy adopted in the design and development of offshore platforms.
This manual provides guidelines for Basic Engineering of offshore platforms and chronicles the various phases of development in the designing aspects, from the initial EIL-developed design criteria followed at the time of inception of the section, to the design criteria currently being adopted by the Offshore Design Section. This manual provides detailed descriptions of the essential design considerations followed by various disciplines of the Offshore Design Section and also covers safety considerations in designing offshore facilities.
This manual when used in conjunction with the Safety Manual, the ISO Manual and the Functional Specifications can provide all necessary inputs to make a functionally complete technical bid package for construction of offshore platforms and pipelines.
Advice and comments from the readers are welcome, and the same shall be taken care of in the future revisions of this document.
(Mr. R. K. Marya)
(Head – Offshore Design Section)
This manual contains information on the Basic Engineering activities related to design of offshore platforms. This manual captures in one place all the design aspects considered in the design of offshore platforms.
The intention of this manual is:
This manual is to be used by the employees of Offshore Design Section, ONGC and other persons so authorized by the Chief Engineering Services. This manual shall be used as a reference document during Basic Engineering of offshore platforms together with the Safety Manual and ISO Manual prepared by the Offshore Design Section.
This manual spans the changes that the Design Criteria has undergone from the time of inception of the erstwhile Engineering and Construction Division in 1992 to its evolution as Offshore Design Section in 2001. A brief description of the constituents of a bid package is covered in this manual.
This is followed by detailed description of the essential design considerations of individual disciplines, including a description on safety considerations in designing offshore platforms. The codes & standards applicable in the design of offshore facilities have been covered appropriately in the design guidelines of various disciplines.
In 1974, with the discovery of the Bombay High field, ONGC entered into a new era of exploration and exploitation of hydrocarbons. It called for creating an infrastructure and facilities for oil and gas field development. The Engineering & Construction (E&C) division was then set up to carryout engineering and construction activities of offshore projects.
At the time of its inception, the E&C division primarily handled Project Management, with engineering activities being executed by reputed engineering consultants such as Lummus Crest Engineering, Snam Progetti and Engineers India Limited (EIL).
Subsequently, a separate section called the Engineering & Planning (E&P) Division was created under the E&C division for conceptualization of schemes, preparation of Conceptual Study Report (CSR), review of basic engineering during bid package preparation and review during detailed engineering and for undertaking engineering studies. While E&P took care of the above-mentioned project related activities, other aspects of the project such as Basic Engineering, preparation of bid package, Detailed Engineering, Yard supervision, installation and commissioning were handled by E&C’s consultant, M/s EIL.
During the year 1984-85, E&P took up engineering for conversion of Jack-up drilling rig “Sagar Vikas” into an Early Production System (EPS) Sagar Laxmi with back-up from CFP TOTAL. Subsequently, in 1990-91 when there was a spurt of development schemes requiring the establishment of 4 process platforms (SHG, NQP, NLP/NLW & SHW) and 13 well head platforms (L-ABCDE, I-MNTWPQS). M/s. EIL expressed their inability to provide consultancy for all these projects in the required time, owing to the enormity of the task. The E&P division was therefore required to undertake the engineering activities in addition to project management activities. This marked the beginning of E&P’s in-house consultancy service for design and construction of offshore platforms.
During the initial stages of transformation of E&P as in-house consultants, the division engaged M/s TRIUNE Pvt. Ltd., New Delhi, as back-up consultants to assist the E&P division in its first engineering consultancy venture - the I-MNTW Project. The basic engineering documents for this project were adopted from the specifications prepared by M/s EIL for similar projects.
From the time of its foray into in-house consultancy services, the E&P division has provided in-house engineering consultancy services for numerous project related to new platforms, modification of existing platforms, submarine pipelines and clamp-on projects as independent consultant, without any back-up.
In 2001, E & P division for the first time took up the consultancy of a process platform project (MNW) – a single largest component of Mumbai High North Redevelopment Scheme. The MNW process platform project being the first platform project to be engineered by E&P, it was felt necessary to employ back-up consultants having adequate experience in engineering process platforms. M/s Worley, Australia were therefore engaged to assist in some of the critical specialty areas (viz. Common FGC Skid, Gas stripping based De-oxygenation system, Living Quarter & structural study, etc.) and to review the bid package for optimization of cost / schedule of MNW Project, participation in the pre-bid conference, review of techno-commercial bid, etc.
In 2002, under the Corporate Rejuvenation Campaign (CRC), the E&P Division was renamed as Offshore Design Section and it continues to provide efficient in-house engineering consultancy.
The foremost activity in the design of offshore platforms is identifying the quantum of work to be executed and finalizing the facilities to be erected and commissioned. These details are compiled to form a bid package which is then issued to prospective contractors. The bid package is prepared on the basis of the Feasibility Report on the project.
Preparation of the bid package is done following approved ISO procedures (compiled by the Offshore Design Section in the form of an ISO Manual) together with inputs from this Design Manual, approved Safety Manual and various Functional Specifications, as well as suggestions / recommendations received from the Operations Group and recognized Engineering Consultants from time-to-time.
(Note: An extract of the Safety Manual and the ISO Manual is given in clause 5.1 and 6.0 respectively of this document)
The bid package includes the Scope of Work of the project, the Design Criteria of various disciplines and the Functional Specifications of various equipment and systems envisaged on the platform.
The Scope of Work describes the quantum and quality of work that is to be carried out. The Scope of Work is unique to every project and is the first document that is prepared when a project commences. (This manual does not cover the basis of finalization of scope of work of a project).
The Design Criteria, which plays a pivotal role in the design and development of the offshore facilities, specifies the essential considerations in the design, procurement, fabrication, transportation, installation, pre-commissioning and commissioning of offshore platforms. It has been a constant endeavour of the Offshore Design Section to improve the design criteria by ensuring that the philosophy adopted reduces platform complexity and cost. (This manual covers in detail the design criteria adopted by various disciplines of the Offshore Design Section in the design of offshore facilities).
The Functional Specifications describe the specific functional requirements of various equipment and systems envisaged under the Scope of Work of the project. (This manual does not include the design details covered in the Functional Specifications of different equipments and systems).
The bid package documents, including the design criteria, used to be generated by EIL in the early 80’s and these were very elaborate and prescriptive. It advocated the use of exotic materials of construction and set higher safety limits, perhaps for achieving higher level of reliability. These additional reliability margins, however, considerably increased the cost, the execution time and the platform complexity. Owing to these, the necessity for optimization was increasingly felt. Therefore, in 1990, an effort was made towards optimization of cost and facilities, simplification and standardization of equipment / systems and deletion of supplementary equipment.
These efforts resulted in a Phase-Wise Optimization process which has help achieve cost optimization by reducing structural tonnage, reducing size of equipment, deleting supplementary equipment and adopting new technology. The outcome of this optimization process has been the establishment of Minimum-Facility Offshore Platforms.
Details of the Phase-Wise Optimization process has been covered in section 3.1 of this manual and the constituents of Minimum-Facility Offshore Platforms (both manned and unmanned) have been covered in section 3.2 of this manual.
As mentioned in section 3.0 above, the phase-wise optimization process was carried out to achieve cost optimization by reducing structural tonnage, reducing size of equipment, deleting supplementary equipment and adopting new technology. The details of the optimizations carried out (with respect to well-head platforms) are as follows:
During Phase I of the optimization process, certain items, which previously formed a part of well platforms, were deleted and the capacity of certain other items were reduced. Details of the same are as follows:
The following items were deleted:
Chemical Storage Tank and Chemical Injection Pumps
Potable Water Tank
Salt Water Tank
Oxygen Scavengers and Bactericide Injection Pump
Phase II of optimization activities began in December 1989 and a report on these activities was submitted in March 1990. This phase of optimization resulted in 250 m2 reduction of platform area and a reduction in structural steel tonnage of approximately 100 t. The total cost saving through this optimization process was approximately Rs. 31.5 million / platform.
The items deleted during this phase include:
I/U Air Compressor in Platform (which is presently sweet)
Space for Future Launcher / Receiver
Nitrogen Back – up for instrument
Air and Fire Water Pump Start – Up
FQS in Gas Lift Instrumentation (flow Totalizer)
Phase III of optimization activities began in January 1990 and a report was submitted in May 1990. This resulted in a cost saving of Rs. 28 million / platform.
The details of the reduction in capacity of items during phase III are as follows:
Машин. Диагностирование гидроприводов mechanisation of construction. Organisation of diagnosis of construction