SOCIETY OF PETROIIW4 ENGINEEW OF AIME 6200 North Centr;;2~pressway =R SPE 1933 Dallas, Texas THIS E A PREPRTNT --- SUBJECT TO CORRECTION Downloaded from http://onepetro.org/SPEATCE/proceedings-pdf/67FM/All-67FM/SPE-1933-MS/2084713/spe-1933-ms.pdf by guest on 28 September 2021 Application of Deep Diving Systems in Offshore Operations By K. G. Young, Reading and Bates Offshore DrilJing CcJ., Tulsa, Okla. @ Copyright 1967 American Institute of Mining, Mctalhwg)ed and Petroleum Engineers, Inc. This paper was prepared for the 42nd Annual Fall Me&ing of the Society of Petroleum Enginee. of IKHIE, to be held in Houston, Tex., Oct. 1-4, 1967. Permission to copy is restricted to an zb- stract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledmcent of where and by whom the .paper. is mwsented. Publication elsewhere af publication in the JOURNAL OF PETROLEUMTECHNOLOGYor tine SOC~EIY OF FETROIWN ENGINEERS JOURNAL usually granted upon req~est ‘to the Editor of the appropriate :ournal provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meting and with the paper, may be considered for publication ill one of the two SFE magazines. ABSTRACT I~TRODUCTIO~ This paper reviews current offshore opera- This paper provides a brief review of deep tions around the world which involve the use diving systems which have current appli- of tethered, manned submersibles to support cations in the support of offshore petroleum deep diving operations. recovery, salvage operations and underwater construction. Its primary focus is on “teth- It discusses the evolution of simple under- eredl, or surface supported diving bell sYs- water transport vehicles to the relatively terns capable of “locking out’’-!i divers sophisticated semi-mobile hydraulic tool rather than submarines (with or without diver equipped, life support capsules which have lockout capabilities), simple observation found applications in offshore petroleum, bells or open bottom decompression rest salvage and underwater construction. A chambers. To date, the tethered diving variety of systems have been developed bell systems with a diver lockout capability, during the past few years to meet the many have enjoyeda more active commercial off- and various needs of the offshore diving in- shore utilization than other types of sub- dustry. mersibles, due to the nature of current off shore technical and economic requirements. The conclusions reachedby this paper are that the current utilization of diving systems The tethered diving bell is an ancient inven- in the support of deepwater offshore work has tion. However$ early diving bell concepts resulted in increased efficiency~ reduced were simple upside-down “teacups” and costs and much safer operations. Al Providing self-contained ambient pres- sure life support 2 APPLICATION OF DEIZP DIVING SYSTEMS IN OFFSHORE OPERATIONS SPE 1~3 generally only provided a life sustaining Three major areas of interest are involved bubble of air for the underwater explorer or in the pressurized respiratory life support worker, The bells which have evolved from of the diver. The first is the problem of this primitive beginning are substantially having to gradually decompress the diver more complex and have been designed to following a dive under controlled conditions include such capabilities as self-contained in order to eliminate the formation of bub - propulsion systems, power for underwater bles in the body by too rapid re -evolution Downloaded from http://onepetro.org/SPEATCE/proceedings-pdf/67FM/All-67FM/SPE-1933-MS/2084713/spe-1933-ms.pdf by guest on 28 September 2021 tools, on-board gas supplies and breathing of inert gas absorbed from the breathing mixture control manifolds, and one atmosp- mixture available to the diver. If the diver here job-site viewing capabilities for supei - is breathing air, the inert gas absorbed is visors and observers while simultaneously nitrogen. placing divers into the underwater environ- ment, The second major area of interest is asso- ,, or stipor producing ciated with the “narcotic It is not economical to provide totally ver- effects of inert gases in the breathing mix- satile capabilities for each job and for this ture under increasing pressure. Argon, reason, a spectrum of diving systems -- for example, is narcotic in proportions some especially designed for specific appli- aimiiar to nitrogen in air at one atmosphere cations -- have been developed over the pressure. Nitrogen becomes slightly nar - past three years, Some of the diving sys- cotic at a partial pressure of approximately tems that have appeared, have not been as four atmospheres (one hundred and fifty universally practical as their inventors had . feet of seawater) and it is very difficult to hoped and there is a current design tendency work with air as the breathing medium at towards developing systems which have more a ?ressure much beyond a depth of two appeal to the user in terms of use-rate eco- hundred and fifty feet of seawater. nomics, ease of installation onto the work or drilling barge, and ability to effectively oper- ordinarily, helium or a combination of ate day and night under the environmental helium and nitrogen is substituted for nitro - conditions imposed by the job. gen as the inert portion of the breathing mix- ture at depths much beyond one hundred and This paper will discuss the technical and eighty feet. Helium is apparently not dan- economic need for deep diving systems in gerously narcotic to a depth of over one context with, current offshore requirements) thousand feet. Unfortunately, one of the and will briefly compare the various types major difficulties in using a light inert gas of diving systems presently available around such as helium is its distorting effect on the world together with current applications diver telephone communications. and experience. ‘The third major ?rea of interest are the upper and lower limits on the partial pres - THE REASON FOR DIVING BELLS sure of oxygen which the diver breathes. The lower limit is established by the oxygen The major promoters of diving bells have required to support metabolic processes, or been divers. There are definite working approximately the partial pressure of oxy- and safety limitations for a diver working gen available in air (approximately three in deep water. The genesis of the “modern” psia). The upper limit is established by diving bell began with diving contractors certain toxicologic effects of oxygen in high attempting to expand their capabilitiess ~o concentrations and is appr ox;mately thirty more effectively work deeper and longer psia for brief periods of time and on the underwater. order of five to seven psia for extended d;rations. W!r those unfamiliar with diving physiology and physics, a brief introduction will be In addition to the above major problem areas necessary to appreciate the problems in- in respiratory life support is the necessity volved in working in deep water and the to maintain a breathing atmosphere free of motivation for diving bell support. SPE 1933 K. G. Young, Jr. irritants or toxic gases such as carbon decompression time for a total saturation dioxide at a Icvel which is compatible with dive at a continuous operational depth of comfort and safety. The diver must also be only 100 feet may be on the order of 24 hours, maintained at a comfortable temperature if the decompression facility must be more his immersion times in cold water are very comfortable (and generally more costly) than long and he must have adequate communi - the facilities required for “partial saturation” cations with the surface to receive instruc - diving. The higher support system costs of tions and as a safety measure. saturation diving techniques must be weighed Downloaded from http://onepetro.org/SPEATCE/proceedings-pdf/67FM/All-67FM/SPE-1933-MS/2084713/spe-1933-ms.pdf by guest on 28 September 2021 against the relatively inefficient! but less In deep water, therefore, the diver control - costly, conventional surface diving techniques. led directly from the surface faces several major problems: rigid requirements on To a depth of approximately 180 feet, mixed control and makeup of the breathing gas, a gas techniques utilizing mixtues of nitrogen controlled rate of ascent with possible ex - and oxygen or nitrogen, helium and oxygen tended decompression in the water, distorted may provide a more economical approach to communications, limited time at depth, and underwater jobs which do not involve many -- in a strong current -- large drag forces consecutive hours of routine work. Total on the diver’s umbilical to the surface, The saturation work to date has shown that about diving bell system doe; not eliminat~ -- but the most work that a diver can perform over at least makes manageable -- these problems. an extended duration is approximately six hours per twenty-four hour period with ‘“ In water deeper than 250 feet or so -- in the about three hours per stretch being an effi - “mixed gas” bi-eathing mixture range -- jt cient maximum consecutive work period. A is generally not practical from an operational major factor in total saturation work is the psychological constraints placed on the diver, safety standpoint to support extended diving operations on submerged wellhead equipment The proper selection of diving crews is also without a diving bell. At less than 250 feet -- of great importance in total saturation job especially with the advent of the faster “gas efficiency. switching” decompression techniques recently being employed, a diving bell capability may It has posed a real problem to those in the prove to be technically unnecessary, depend- diving and diving systems business to dem - ing on such factors as current, weather, dril - onstrate to the offshore industry that divers ling difficulties, etc.