Bilinear Flow in Horizontal Wells in a Homogeneous Reservoir

Topics: Directional/extended reach wells
Fig. 1: Simulation data of three-layer model with nonuniform vertical permeability matching closely with well data. Inset: graphical representation of dimensions and well parameters used in the simulation model. KV, KX, and KY=vertical, minimum horizontal, and maximum horizontal permeability, respectively. L=effective horizontal well length.

In the Huntington field in the North Sea, bilinear flow with a clear one-quarter slope in the pressure derivative has been observed during intermediate times in horizontal-well tests, instead of the usual linear flow with a one-half slope expected in a homogeneous reservoir. This paper offers insight into an integrated effort at combining analytical information, numerical well-test models, and geological evidence to explain the reservoir behavior observed in the Huntington field.

Reservoir Description

The Huntington field is a sandstone reservoir with a maximum oil-column thickness of 120 ft, located within a sand-rich turbidite system in the central North Sea. Vertical appraisal wells show a largely homogeneous reservoir with average porosities of 20%, net/gross ratio of 80–90%, and average permeabilities of 30–60 md. Core samples do not indicate any inherent natural fractures.

The reservoir contains undersaturated light oil with gravity of 43 °API, viscosity of 0.3 cp, and bubblepoint pressure of 2,200 psig at reservoir pressure of 4,000 psig and temperature of 250°F. Well tests of two vertical wells match a homogeneous-reservoir model, but four horizontal producers drilled in this reservoir exhibited a one-quarter-slope straight line in the pressure derivative, stretching up to two log cycles during intermediate time.

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 174325, “Bilinear Flow in Horizontal Wells in a Homogeneous Reservoir: Huntington Case Study,” by Wei Cher Feng, E.ON E&P; Peyman Nurafza, BG Group; Basil Al-Shamma, E.ON E&P; and Alain Gringarten, Imperial College London, prepared for EUROPEC 2015, Madrid, Spain, 1–4 June. The paper has not been peer reviewed.
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Bilinear Flow in Horizontal Wells in a Homogeneous Reservoir

20 October 2015

Volume: 67 | Issue: 11