Minimum Area Rig Concept Update: H and P 101 Modifications and First Infield Move
Authors: Sigurdson S.R. 
Published: December 2007

Summary.
The minimum area rig concept (MARC) is a cost-effective alternative to the typical self-contained platform rig (SCPR). Helmerich and Payne (H and P) built the first MARC rig, H and P 101, to drill and to work over wells up to 16,000 ft [4877 m] measured depth. This rig began operation in May 1983 in the Gulf of Mexico at Arco Oil and Gas Co.'s South Pass Block 61 field and has undergone one infield move. Since the rig's initial mobilization, several rig modifications have been added to increase storage area, to promote safety, to provide a more efficient drilling/workover rig, and to reduce overall move time. This paper describes the modifications and recaps the rig's first move. This will provide further insight into the MARC rig and show the benefits of the MARC design in relation to a move.

Introduction
H and P Rig 101 was designed, contracted, and built to work in the South Pass 61 field. The rig was mobilized initially in May 1983 and has proved to be the most efficient offshore drilling/workover rig in service in our Southeastern Dist. A savings of $1.4 million/yr over an SCPR has been realized as a result of lower day rate (lower initial investment) and mobilization/demobilization costs. The MARC design was needed in the operator's offshore environment to facilitate drilling and workover operations on producing platforms. All the platforms in the South Pass Block 61 field have production equipment on the drill deck (i.e., quarters and compressors), leaving approximately 75 % of the deck for a drilling/workover rig. Consequently, a rig was needed that would fit in the limited space but would still have the capabilities to drill and to work over up to 16,000-ft [4877-m] directional wells. (See Figs. 1 and 2 for original rig layout.) Economics was also an important criterion considered in the MARC design.
The MARC rig design was planned to service the operator's platforms easily, yet eliminate an expensive derrick barge for each move. As a result, the "leapfrog" crane concept was used, whereby the crane that offloads the rig from the barges to the platform serves as the rig crane through the next move. H and P Rig 101 was mobilized initially on South Pass Block 60 Platform D, performed 12 workovers, and drilled eight wells. Modifications to the rig have been made, and the rig has moved to other platforms. This paper documents the modifications and the first move.

Rig Modifications
The deficiencies with the original MARC design evolved around the limited available space and resultant space use. Modifications were proposed to add badly needed storage area and to improve the overall efficiency of drilling, workover, and moving operations. We contracted IMI Engineering, the firm that originally designed the rig, to perform a third-party engineering evaluation of what improvements could be made without exceeding existing load limits. We requested that IMI submit a turnkey bid for construction and supervision through installation of the approved modifications. Construction-grade drawings were made, and after a final meeting, work on the modifications began. The following is a description of each modification.

Drawworks/Wireline Shed.
One of the most apparent areas in need of improvement was a permanent position for an electrical wireline unit. The skid-mounted units being used were costing the rig up- and downtime, and damages were occurring during transport and handling. Also, covered storage was limited on the rig. As a result, a drawworks/wireline shed was designed to fit on the back porch of the rig floor. This shed incorporated a permanent position for an electrical wireline unit, a covered storage area in a place that was previously open to the weather, and a mast stand that is needed to rig up or down the derrick. The shed was welded to the back porch. so it did not add a lift during moves. The wireline unit was installed on top of the shed and is out of the way during normal operations (Fig. 3). Besides supplying a covered storage area for small tools, the shed protects the previously open rig floor from weather.

Mud Logger Floor.
The permanent mud-logging unit consumed too much space in its original location, the "hole" on the drill deck between the pipe rack and rig structures. It was left rigged up when possible, regardless of whether completion or workover operations were in progress. This was taking up valuable equipment storage space, however, especially during gravel packs, and was unsafe (approximately 50% of the crane lifts passed over the unit).
JPT
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