Many simulation studies were conducted about the importance of perforated welllength 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 modelsbefore 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 (60cm × 40 cm × 20 cm) was designed and used to achieve the study objectives. Carefully sized sandpacks were used to represent the homogeneous unconsolidated porous media while aperforated aluminum sheet was used as ahorizontal 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-fracturedformation vertical to well axis improve productivity of horizontal well for different perforation ratios. A single vertically-fractured porous medium provides higher productivity ratiothan 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 dropalong horizontal well may haveserious implications on perforated well length since proportionality of the productivity index to the well length is no longer valid.
Recently the economic feasibility of drilling a horizontal well improved drastically due to advances in drilling technology. Advantages of horizontalwell over vertical well applications have been confirmed by many scientists(1)(2)(3)(4) and operators(4)(5)(6). Horizontal wells showed many distinct advantages over the vertical ones such as improvement of well productivity, attenuation of sand production, and significant reduction of gas and/or water coning problems.
From reservoir and production engineering standpoints, the sole difference between vertical and horizontal well is identified to be the contact area. Fora partially penetrating vertical well, the reservoir disturbance due to avertical well is limited to the close vicinity of the well borehole(7)(8)(9). Then, the choke diameter becomes the main parameter affecting the flow rate. For a horizontal well, the disturbance created by the well is not limited only to the vicinity of the wellbore but also influences the whole reservoir due to the greater contact area of the pay zone penetrated by the well.