Injectivity of Frac-Packed Wells: A Case Study of the Guando Field

SPE Production &Amp; Operations

2014

The filtration of solids in the injection water in a frac pack is the primary factor controlling the injectivity decline in frac-packed waterinjection-well completions. The injectivity may decline rapidly or much more slowly, depending on the degree of frac-pack filtration. The widening and lengthening of frac packs and the associated loss of sand control are affected also. However, there are no experimental data available for the filtration coefficient at high velocities that are typical in frac packs. In this research, the filtration coefficients were measured experimentally in high-velocity flows encountered in frac packs. The solid concentrations and pressure drops across proppantpack sections were measured and correlated with earlier filtration theory and permeability-decline models. The filtration coefficients were measured at various flow rates and for different proppant sizes. Our experiments show that at high fluid velocities, the filtration coefficient is significantly lower than that estimated from prior correlations that are based on low-velocity filtration.We have developed new empirical correlations for filtration coefficients at high flow rates in frac packs. The improved filtration coefficients were used as the primary input into a well-injectivity model. The proper estimation of the filtration enabled us to more accurately analyze the impact of injection rates and proppant selection on injector performance (i.e., predict long-term injection-well behavior). The effect of particle filtration in the frac pack, and its effect on injector performance, was captured accurately for the first time. The newly presented empirical correlations coupled with a model for frac-pack growth in the injection well allowed us to estimate accurately the fracture dimensions and the long-term water injectivity of frac-packed injectors. These results can be used for frac-pack design, proppant selection, and specification of injection-water quality.Effect of Frac-Pack Filtration on Injectivity. Suspended particles in the injection water can be deposited by various modes of

Section: Background On Filtration In Frac Packsmentioning

confidence: 99%

Filtration in Frac Packs and Its Impact on Injector Performance

Hwang

SPE Production &Amp; Operations

2014

“…The pressure at the tip is dependent mainly on the injection rate and if that is reduced the fracture will tend to close. Based on a recent history match study (Suri et al 2010), it is believed that reduction in fracture length (fracture closing) and reopening does occur in injection wells.…”

Section: Fracture Closurementioning

confidence: 99%

Estimates of Fracture Lengths and Injection Profile in an Injection Well by History Matching Bottom Hole Pressures

Suri

Proceedings of SPE Western Regional Meeting

Peters

2010

An injection well model is presented that can be used to history match a field injector's bottom hole pressure (BHP) taking into account particle plugging due to injected solids, poro-elastic and thermo-elastic stresses, increase/decrease in injection induced fracture lengths, injector shut-ins / re-starts, changes in injection rates and average reservoir pressure. Estimates of fracture lengths and injection profile as a function of injection time are predicted for a field injector in a multi-layered reservoir. The solids deposition is modeled accurately using filtration theory; the flow of the injection fluids is modeled using approximated composite zones (3 zones with uniform saturation and mobility) and the pressure at the wellbore is calculated using Gringarten's infinite conductivity fracture solution. The injection induced fracture lengths are calculated based on Perkins and Gonzalez fracture propagation model (1985) that accounts for the thermal and poro-elastic stresses. The model is a semi-analytical simulator that can predict injector performance through history matching an injectors' daily record of injection rate and BHP. More reliable future estimates of injectivity, skin, fracture lengths in a multi-layered reservoir, front locations, and injection fluid profile can be obtained. Both short term pressure transients and long term pressure transients observed over several years of injection need to be history matched to capture effects that are important at both short and long time scales. Finally an example field case study is presented where BHP and injectivity of an ongoing injection well is history matched for both a few short term injection time intervals and over a period of 3 years. It is shown that both the solids deposition and the opening/closing of the injected induced fractures need to be accounted to obtain a good history match. These processes controlled by the layer stresses and the water quality are the most important physical processes determining the injector's injectivity and injection profile.

Estimates of Fracture Lengths and Injection Profile in an Injection Well by History Matching Bottom Hole Pressures

Suri

SPE Western Regional Meeting

Peters

2010

An injection well model is presented that can be used to history match a field injector's bottom hole pressure (BHP) taking into account particle plugging due to injected solids, poro-elastic and thermo-elastic stresses, increase/decrease in injection induced fracture lengths, injector shut-ins / re-starts, changes in injection rates and average reservoir pressure. Estimates of fracture lengths and injection profile as a function of injection time are predicted for a field injector in a multi-layered reservoir. The solids deposition is modeled accurately using filtration theory; the flow of the injection fluids is modeled using approximated composite zones (3 zones with uniform saturation and mobility) and the pressure at the wellbore is calculated using Gringarten's infinite conductivity fracture solution. The injection induced fracture lengths are calculated based on Perkins and Gonzalez fracture propagation model (1985) that accounts for the thermal and poro-elastic stresses. The model is a semi-analytical simulator that can predict injector performance through history matching an injectors’ daily record of injection rate and BHP. More reliable future estimates of injectivity, skin, fracture lengths in a multi-layered reservoir, front locations, and injection fluid profile can be obtained. Both short term pressure transients and long term pressure transients observed over several years of injection need to be history matched to capture effects that are important at both short and long time scales. Finally an example field case study is presented where BHP and injectivity of an ongoing injection well is history matched for both a few short term injection time intervals and over a period of 3 years. It is shown that both the solids deposition and the opening/closing of the injected induced fractures need to be accounted to obtain a good history match. These processes controlled by the layer stresses and the water quality are the most important physical processes determining the injector's injectivity and injection profile.