Postma_E&P_quark6_Outsourcing_book_temp.qxd 12/11/2009 13:14 Page 76
Marine Operations During Transport and Discharge of SPAR Hulls
Figure 5: Perdido SPAR Aboard the Dockwise Semi-submersible Vessel Mighty Servant 1
truss structure and this load will have to be spread over a large Octopus On-board Motion Monitoring System
deck area, which requires large supporting structures. To meet Increases Journey Safety
the vessel longitudinal strength requirements, the vessel has to With daily reports sent from the HTV to a central database server,
be ballasted. clients can be informed about the location and status of their property
using a web-based information system. After the voyage, recorded
The summer loadline draft may not be exceeded in this condition. data are evaluated and the impact on the cargo can be analysed.
Taking into account the water depth of the approach to the loading Results can be reported to the client. With this information, during the
location and mean water and maximum water level fluctuations due to voyage clients may perform a fatigue assessment, for example.
wind, the minimum expected water depth is determined.
Vessel Hull and SPAR Hull Deflection and
Unrestricted departure is possible only when this minimum expected Their Interaction
water depth is at least more than the minimum vessel draft and Because the SPAR is relatively stiff, high local loads are induced in the
required safe UKC. However, for the loading location channel HTV and the SPAR. This has been identified as a critical aspect and
will affect the support and sea fastening design. Interaction between
the SPAR and the transportation vessel during the voyage, with
For a large SPAR, calculations
respect to load distribution and local and global deformations, needs
to be investigated.
show that discharge without
any additional stability aid
Deck loads induced by hogging and sagging conditions or loads on the
results in insufficient stability
heave plate supports resulting from torsion in stern quartering seas
must be assessed. Both structural evaluations vary on a case-to-case
during at least part of the basis, and unfortunately no general conclusions can be drawn from the
operation, and additional
executed projects.
stability devices are required.
During the Discharge Phase
Potentially critical aspects have been identified and evaluated in this
chapter based on the assumptions below.
passage the vessel can be ballasted to a reduced draft while meeting
the longitudinal strength criteria for sheltered condition. Once the the SPAR weight after discharge includes the support weight;
vessel has passed the channel, she must be ballasted to voyage the cradle comes off with the SPAR;
condition. Even when the HTV is in a light ballast condition the cribbing height on vessel is 600mm; and
passage will, in most cases, need to be modified in order to the discharge is at a sheltered location.
accommodate a vessel UKC of 1.0m. Note that the minimum draft is
strongly dependent on the weight and weight distribution of the Note that the SPAR supports are assumed to stay connected to the
SPAR on the vessel. Different weights and weight distributions may SPAR hull after discharge (included in the SPAR weight after discharge).
result in deeper drafts. This is as per earlier executed projects.
EXPLORATION & PRODUCTION – VOLUME 7 ISSUE 2
76
Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103  |  Page 104  |  Page 105  |  Page 106  |  Page 107  |  Page 108  |  Page 109  |  Page 110  |  Page 111  |  Page 112  |  Page 113  |  Page 114  |  Page 115  |  Page 116  |  Page 117  |  Page 118  |  Page 119  |  Page 120  |  Page 121  |  Page 122  |  Page 123  |  Page 124  |  Page 125  |  Page 126  |  Page 127  |  Page 128  |  Page 129  |  Page 130  |  Page 131  |  Page 132  |  Page 133  |  Page 134  |  Page 135  |  Page 136  |  Page 137  |  Page 138  |  Page 139  |  Page 140  |  Page 141  |  Page 142  |  Page 143  |  Page 144  |  Page 145  |  Page 146  |  Page 147  |  Page 148  |  Page 149  |  Page 150  |  Page 151  |  Page 152  |  Page 153  |  Page 154  |  Page 155  |  Page 156  |  Page 157  |  Page 158  |  Page 159  |  Page 160  |  Page 161  |  Page 162  |  Page 163  |  Page 164