Offshore Horizontal Technology Increases Field Life And Monetary Savings
Authors: Leaf R.C. , Pittard F.J. 
Published: October 2008

As offshore oil fields mature, enhanced oil recovery may be facilitated through the use of horizontal and extended-reach directional drilling.

Slim-hole motors are currently used offshore to extend the vertical and directional depth of existing boreholes. These boreholes supply hydrocarbon information through geological zone isolation.

As this information shows potential for hydrocarbon enhancement, horizontal technology and when needed enhanced oil recovery (EOR) methods may combine to further develop the mature offshore oil field.

This paper goes into the description of offshore horizontal technology; bottom hole assembly (BHA) units and gee-guidance tools as they make for positive economics when applied to geological zones in the mature offshore oil field.

INTRODUCTION:

Horizontal drilling offsets economic decline as it enhances hydrocarbon production within the mature offshore field-making positive economics a reality.

STATEMENT OF THEORY AND DEFINITIONS:

In theory, greater exposure of the production zone via the wellbore increases hydrocarbon productivity while increasing monetary gain.

This theory can be applied to the offshore mature field with respect to; vertical deepening, extended-reach drilling (ERD) as applied to workovers, multi-lateral directional well applications, and new horizontal drills.

Offshore vertical deepening can be defined as a type of ERD drilling. The effect of ERD is to extend the directional well into new geological zones. Potential hydrocarbon production data gathered from these zones will then determine if these regions are further developed.

Horizontal drilling maximizes hydrocarbon production when properly applied to feasible (ERD) regions, These regions then enhance production offsetting hydrocarbon decline within the mature offshore field, thereby, increasing hydrocarbon producability and field life.

The radius should be considered prior to horizontal application, For radius selection, see table I, The radius type is dependent on formation geology and selection of well application; new drill, workover, or extension. The radius of choice is then set from the kick-off point (KOP) taking into account geology and type of reservoir.

There are two types of reservoirs of which other reservoirs are composed in combination or in whole; the heterogeneous and homogeneous reservoir, see fig 1. and fig 2.(Available in full paper)

In either the heterogeneous or homogeneous reservoir, horizontal section maximization maximizes hydrocarbon production. When horizontal technology is properly administered, it produces positive economics offsetting hydrocarbon decline in both the heterogeneous and homogeneous field.

Maximum horizontal displacement in the homogeneous field means; more hydrocarbon surface area exposed to the producing wellbore, decreased specific area concentrated drawdown, decreasing water coning effect on the producing section of the wellbore, and increasing the productivity index (PI).

In the mature offshore heterogeneous field, horizontal drilling optimizes hydrocarbon fracture penetration improving producability and enhancing monetary gain. This is achieved by drilling horizontally in the direction of minimum stress, thereby maximizing hydrocarbon fractures penetrated, see fig 1(Available in full paper).

Prior to horizontal development of the mature offshore field, caution must be maintained with respect to; horizontal section length, geological dip of formations, location of hydrocarbon regions, optimum permeability depth, fracture azimuth, productivity index (PI), and all other reservoir specific properties.