The Dynamic Bottomhole Pressure Management: A Necessity to Gravel Packing Long Horizontal Wells With Low Fracture Gradients

摘要

Unconsolidated formations are commonly found in offshore reservoirs where long and ultra-long horizontal wells are required to produce heavy oil economically. The main characteristics of these reservoirs include high permeability, large porosity, low fracture gradients and sand production. Gravel packing is proven as an efficient and cost-effective sand control practice for these completions and formations. The quality of the gravel pack and effective sand control play a major rule on the ultimate success of oil and gas production from these reservoirs. Successful placement of the gravel pack completion requires that these low fracture gradient wells not be fractured during gravel placement to avoid excess leak-off and premature screenouts. This paper addresses several key factors that must be considered carefully in installing a successful gravel pack completion. The dynamic pressure management scheme becomes critical to maintain the bottomhole pressures in the required range for a successful implementation of the gravel pack. These include designing an optimal screen-wash pipe annulus during Alpha-Beta wave packing, an optimal Alpha wave height, the use of mechanical device to reduce frictional pressure during Beta wave building up, and the use of multiple Beta wave packing rates. Several job designs and application histories are also presented in the paper to demonstrate the design considerations and valuable lessons learnt. The overall system of fluid dynamics is discussed and treatment guidelines are presented to provide the Completion Engineers the necessary information for designing successful treatments.