Abstract

During performance of a recent experimental whipstock testing program, a procedure was requested in which the whipstock was to be retrieved and the lateral cemented back to provide parent-bore integrity. This paper will describe the problems experienced in attempting this procedure as well as the method subsequently developed to successfully abandon the openhole that had been drilled from a window in the cased wellbore. Included will be the problem statement, job design, planned procedure, job execution, and results.

The test program required the lateral to be accessed for plugging after the whipstock had been retrieved. The initial design solution was to use a bent joint of drill pipe with a bent sub on bottom to access the lateral bore. Following several attempts, it was found to be impossible to reenter the lateral with the designed bottomhole assembly (BHA) from the 32-degree parent wellbore.

To address the problems, a new procedure was designed to set a balanced plug across the window using open-ended drill pipe, and then, to squeeze the cement into the window. This procedure provided the capability to accomplish the task.

Of particular significance is the fact that a combination of simple, previously used concepts was applied to a new application to provide an innovative solution. The combination includes high and low pressure, hesitation, and braden head squeeze procedures. This method can be applied to similar scenarios that will undoubtedly surface as usage of the new multilateral completion techniques becomes more prevalent.

Introduction

The wellbore conditions and procedures described in this paper were executed in Well 22-2X10 in Section 10, T39N R78W in the Teapot Dome Field, Natrona County, Wyoming on December 8, 1996. This field is owned by the U. S. Department of Energy and is operated by Fluor Daniel (NPOSR), Inc. under contract #DE-AC01-92FE62316. All information presented in this paper and associated with this test is in the public domain. The testing procedure was initiated by an Engineering/Manufacturing company involved in the development of a hollow whipstock for use when a lateral liner is mechanically connected to a parent wellbore and communication with both wellbores is desired.

Occasionally, there are instances when a window is milled into casing for sidetracking, horizontal reentry, or multilateral applications, and then, the window is no longer desired. This need could occur from the inability to find a reservoir target, a mechanically obstructed hole, a change in plans, or as in the case of a test scenario, the testing of a new technology. In this case, the testing that involved the construction of the window had been completed. The window was no longer needed as the main, or parent, wellbore was to be used for other testing purposes and would be required to contain wellbore pressures during subsequent drilling and completion operations.

In the method developed to remove the whipstock, the window was broken down, and an injection rate was established with mud, similar to a high pressure squeeze. The balanced plug was then circulated in place across the window. The drill pipe was pulled up above the plug, and excess cement was reversed out with two drill pipe volumes of mud. The pipe rams were closed and pressure applied down the drill string to squeeze the cement into the window, utilizing conventional procedures for low pressure and hesitation squeeze jobs.

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