This paper presents a comprehensive review of current petroleum literature focusing on the reservoir engineering petroleum literature focusing on the reservoir engineering aspects of horizontal well technology. The objective of the paper was to provide the engineer/scientist with an overview, paper was to provide the engineer/scientist with an overview, discussion, and where appropriate, recommendations for the following areas:
analytical solutions for one-phase flow;
water or gas cresting;
numerical simulation;
hydraulic fracturing; and
well test analysis.
Some of the more simple equations are given in the paper, while complex solutions are thoroughly referenced for detailed study.
Over the past several years, horizontal wells have become the "hot" topic of the oil industry. The review paper by Joshi in mid-1987 sparked the interest of major oil companies and small independents alike. By late 1990, it seemed that every operator had a horizontal well project planned or on-line in some area of the world. Because of the planned or on-line in some area of the world. Because of the interest, economics, and publicity surrounding horizontal wells and the presence of significant gaps In horizontal well technology, a large amount of recent research has been focused on the topic, much of it in the area of reservoir engineering.
Recent work In the area of analytical solutions for productivity and transient pressure response has emphasized productivity and transient pressure response has emphasized various boundary conditions. These boundaries are not just the lateral reservoir boundaries as with vertical wells, but the top and bottom (vertical) boundaries encountered in the three-dimensional nature of flow to a horizontal well. Near wellbore effects, such as formation damage, non-Darcy flow, and arbitrary completion have been recently addressed. Some attention has also been given to predicting inflow performance relationships (IPR's) for horizontal wells.
Transient pressure theory has been extended to account for various boundary conditions, to generate derivative responses, and to define the pressure response of a horizontal well in a naturally fractured reservoir.
Advances In simulation models have focused on the problems encountered in simulating the complex problems encountered in simulating the complex three-dimensional flow to a horizontal well. These problems Include grid refinement and wellbore hydraulics. Water and gas cresting has been addressed using both simulation models and simplified analytical expressions.
Enhanced oil recovery was one of the original areas of application for horizontal wells. Recent work in EOR examines steam flooding and methane recovery from coal seams.
Perhaps one of the more interesting areas of study is hydraulic fracturing aspects of horizontal wells. The fracturing process itself, models for predicting production, optimization process itself, models for predicting production, optimization procedures for the number of fractures, and early time procedures for the number of fractures, and early time transient response of fractured horizontal wells have only recently been given attention.
Each of these topics are discussed In a corresponding section. it is the purpose of this paper to summarize and update the Industry on progress In reservoir engineering of horizontal wells since Joshi's review.
P. 403
