spe-rgce case studies

8/9/2019 SPE-RGCE Case studies

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INTRODUCTION

Aim of this study is to reduce the drillingcost in ultra deep water by usingmodified second and third generation

rigs other than fourth and fifthgeneration.

This study focuses how to reduce the

environmental pollution in deepwaterconfigurations in case of riser failure.


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STUDY FIELD

Block = Donggaladeepwater block,

OffshoreMahakam straight,

Indonesia.

Rig type = second and

third generation(jack up rig)


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Drilling data

Total Depth = 13,000 ft

Water Depth = 6,000 ft

Well plan Conductor casing= 13 3/8 inch

Surface casing = 11 inch

Intermediate casing = 9 5/8 inch

Production casing = 7 inch


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PROBLEM IN THE WELL

Surface casing had to be set higherthan planned to avoid penetrationinto the shallow gas zone.

Well plan need to be changed


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OPTIONS AND THEIR

LIMITATIONS Option 1:drilling ahead and setting the 95/8-in. casing

followed by the 7-in. casing string.

Problems: After setting the 7-in. casing string higher than

was called for in the well plan, had to drilldeeper using smaller casing sizes.

The smaller hole would have to be drilled usingslim hole tools, which would have presented thedifficulty of a smaller internal diameter at TD

Difficulty in logging and testing for formationevaluation


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Option 2:

To plug and abandon the well andcontinue exploration in a different

areaOption 3:

To start with a larger conventional

casing size to maintain adequate holesize in the target zone.

Limitation: Require more rig size capacity


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SOLUTION :EXPANDABLE

OPEN HOLE LINER A 1,300-ft string of 95/8113/4-in. solid

expandable open hole liner was run to

depth and set at 9,400 ft. Liner expansion was performed with

hydraulic pressure up the liner.

As each stand of drill pipe was removedfrom the hole, the pressure was bled off,and the stand was broken out andracked back in the derrick.


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The process of reconnecting the topdrive and resuming upward expansionwas repeated until the entire liner had

been expanded and sealed

The liner was pressure tested to 1,000psi for 30 minutes.

The expansion cone was then pulledout of hole, and the float shoe wasdrilled out.


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RESULT:

Installation of an expandable linerenabled to get back on the originalwell plan and

Reached the target zone withadequate wellbore size.


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PROBLEM 2

Fear of environmental pollution dueto riser failure in the surface stackBOP

Loss of mud in the ocean floor.

High cost of drilling per well


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OPTIONS & THEIR

LIMITATIONS Option 1: Use of subsurface BOP stack to prevent

riser failure and use of low pressure riser

Limitation: Require fifth generation drilling rig (drill

ship) with the typical day rate increase upto 2oo,000 $/day

Option 2: Use of surface stack BOP and high

pressure riser Limitation: More chance for riser failure


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SOLUTION : ENVIRONMENTALSAFEGUARD SUBSEA SHUTOFFVALVE

Offers a practical means of

disconnection in an emergency. Capability to shear, seal, and

disconnect from the seabed;

In an unplanned disconnect, therelease of mud from the riser intothe sea is reduced by nearly 60%.


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RESULT

The implications of using thistechnology combination extendbeyond project cost; operators cannow reach ultra deepwater targetsusing a wellbore size that waspreviously possible only by use of

subsea-BOP technology.


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ADVANTAGE

Use of a high-pressure riser as opposed toa low-pressure riser used with fourth- andfifth-generation rigs.

Lower mobilization costs. Significant reduction in day rates.

Less fuel consumption.

Reduced mud volume.

Lower bit costs based on smaller holesize.

Reduced casing cost as a result ofeliminating a number of strings.


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