Sand Control during Drilling, Perforation, Completion and Production

Abstract

Sand control has been a challenge to the petroleum industry since oil and gas was produced from weakly cemented sandstone formations. Several techniques have been applied;restricted (critical) production rate,screen and/or gravel packing,sand consolidation,FracPacking,oriented and/or selective perforation, andcombination of any of the above. Sand formations may fail in compression, tension, and cohesion that trigger sand production. The compressive failure occurs during drilling where the rock cannot withstand the new stress field and/or the cementation materials have deteriorated from mud filtrate exposure. The calculation of mud weight to prevent compressive failure will be presented in this paper. Additionally the failed zone is usually oriented in the direction of minimum horizontal stress which can be avoided during perforation by orienting the perforation tunnels in the direction of maximum horizontal stress. During completion the cementation materials should be protected from completion fluids. During production a pressure drawdown is established for a given production rate. This pressure drawdown may cause rock failure in tension or cohesion (erosion) leading to sand production. The near-wellbore pressure is caused by skin damage due to reduced permeability, stressed region, convergence flow, and partial penetration. This paper presents a model to determine the critical pressure drawdown based on relating the near-wellbore pressure drawdown to the tensile and cohesive strengths of the formation. Hydraulic fracturing, referred to as FracPack, may be applied to alleviate the near-wellbore pressure drawdown below the critical value that causes sand failure. Two fracture parameters are designed to achieve this goal; fracture length and fracture conductivity. This paper presents a design criterion to determine these parameters to optimize a FracPack design for sand control. Examples from a field in Saudi Arabia will be used to validate the application of controlling sand production using screenless FracPack completion. In these wells a FracPack treatment alone controls sand production. The multirate test used in these wells and the FracPack design for fracturing treatments will be presented. Introduction Sand production has historically been a problem associated with soft or poorly consolidated formations. The result is usually lost production due to formation sand and fines plugging gravel packs, screens, perforations, tubular, and surface flow lines or separators. In addition to damaging pumps or other downhole equipment, erosion of casing and surface facilities may also occur. Sanding problems may actually cause loss or recompletion of a well due to casing and/or hole collapse. The methods applied to minimize the effect of sand production include critical production rate, gravel packing, sand consolidation, FracPacking, oriented and/or selective Perforation, expandable sand screen, or a combination of these methods. Completion methods are selected based on sand characterization and failure mechanism. Laboratory testing and mathematical models used for sand prediction are selected based on sand characterization. FracPac completion has been replacing gravel packing in many petroleum reservoirs. However FracPack with a screen in hole, is also widely applied. This paper will discuss the process of sand control from the time a given formation is exposed to man's disturbance and will sicuss sand control during drilling, completion, and production.

Sand production simulation under true-triaxial stress conditions

“…For example, the density of the formation is directly proportional to the in situ stresses, or the permeability is proportional to the effective porosity. Many articles have been published on the effect of porosity on formation instability, all of which confirm a larger failure potential in formation with higher porosity (Abbas et al, 2003;Gil et al, 2005).…”

“…This mechanism is the typical failure in the case of poorly consolidated sands. Cohesive failure occurs when the drag force, due to fluid velocity, exceeds the cohesive strength of formation at the perforation tunnel wall (Abbas et al, 2003). The cohesive strength in unconsolidated sands is close to zero; therefore cohesive failure is the main failure mechanism in these formations.…”

“…This mechanism is the typical failure in the case of poorly consolidated sand. Cohesive failure occurs when the 845 drag force due to fluid velocity exceeds the cohesive strength of formation at the perforation tunnel wall (Abbas et al, 2003).…”