Influences of perforated length and fractures on horizontal well productivity: An experimental approach

Many simulation studies were conducted about the importance of perforated well length on horizontal well performance. All of these studies suffered from their dependence upon theoretical models, which lack plausibility due to the lack of accurate experimental and/or field data. Therefore, there is a real need for experimental data to be used for tuning the single well simulation models before applying a full field simulation of oil reservoirs with horizontal wells. This experimental study was designed to investigate the influences of fraction of perforated length, total length, and fractures, which do not intersect with well axis, on the productivity of horizontal wells. An experimental model (60 cm X 40 cm X 20 cm) was designed and used to achieve the study objectives. Carefully sized sandpacks were used to represent the homogeneous unconsolidated porous media while a perforated aluminum sheet was used as a horizontal fracture parallel (horizontal fracture) and perpendicular but not intersecting (vertical fracture) the horizontal well axis in sandpack. Eighteen runs for porous media with and without fracture systems were carried-out using horizontal wells with different lengths and different perforation fractions of total length. The results indicated that the increase of perforated well length increases flow rate of the horizontal well for both homogeneous and fractured formations that do not intersect with well axis. Furthermore, horizontally-fractured formation parallel to and vertically-fractured formation vertical to well axis improve productivity of horizontal well for different perforation ratios. A single vertically-fractured porous medium provides higher productivity ratio than horizontally-fractured one for the same perforation length and intensity, when both fracture systems do not intersect with well axis. Several empirical equations were developed to correlate the horizontal well productivity with perforated length for homogenous and fractured porous media. Ignoring effects of fractures and pressure drop along horizontal well may have serious implications on perforated well length since proportionality of the productivity index to the well length is no longer valid.