RIASSUNTO
ABSTRACT
Two wells extending out over two miles have been drilled by Union Oil Company of California (Unocal) from Platform Irene in the Pt. Pedernales Field, offshore California. These wells hold the record for the two longest reach wells on the West Coast.
Several wells around the world have been drilled beyond two miles, but none have accomplished this feat at such shallow, true vertical depths. The average angles (from rotary table to TD) for Platform Irene wells A-16 and A-17 are 70.9° and 68.2°, respectively.
This paper will present to the industry the concepts of a ""Negative Weight Well"" and ""Drag Risk Analysis"", and will focus on the innovative technology used to drill and complete a high drag well. The successful drilling and completion of these wells has enabled the future recovery of millions of barrels of oil originally expected to be produced from a second platform.
INTRODUCTION
Unocal and its partners, Gulf (now Chevron) and Superior (now Mobil), acquired Federal Lease OCS P-0441 in OCS Sale #53 in May, 1981. The Pt. Pedernales field was discovered in November, 1982 with the drilling of Unocal OCS P-0441 #1. Platform Irene was set in August, 1985 and the first well was spud in April, 1986. In March, 1987, tracts P-0437, P-0438, P-0440, P-0441, P-0444, and P-0510 were combined to form the Pt. Pedernales Unit consisting of seven partners.
Platform Irene is located in 242' of water approximately 4.5 miles from nearest land and 60 miles west-northwest of Santa Barbara, California.
Figure 1 depicts Platform Irene's location relative to the California coastline.
FIELD DEVELOPMENT
A viscous 15.8° API crude oil and gas are produced from the Miocene Monterey formation. The Monterey varies several hundred feet in thickness and consists of vertically fractured, thin-bedded and interlaminated cherts, dolomites, and shales.
Production was initiated in April, 1987 at the rate of 10,500 BOPD, 0% cut. Peak production of 23,500 BOPD was achieved in August, 1987 after eleven development wells were acidized.
It was originally intended to develop the south-east portion of the reservoir with Platform Irene and set another structure, Platform Iris, approximately two miles to the north-west, to develop the rest of the field. The setting of Platform Iris became uneconomic s oil prices plummeted.
OBJECTIVES
By drilling the high angle, extended reach wells from Platform Irene, it was hoped that the following objectives would be achieved:
The need for the high capital costs of a second platform would be eliminated.
The near-horizontal well bores would intersect more vertical fractures and cut more formation.
Prove that not only could a ""Negative Weight Well"" be drilled and completed, but that it could be accomplished in an economic manner.