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sand production - an overview | sciencedirect topics

On the basis of the rock failure theory, when the compressive strength of rock is lower than the maximum tangential stress σt, the borehole wall rock is infirm, thus leading to the structural failure of rock and rock matrix sand production. The discriminant for determining whether the borehole wall rock of a vertical well is firm is as follows:

where σt is maximum tangential stress of borehole wall rock, MPa; C is compressive strength of formation rock, MPa; υ is Poisson's ratio of rock, decimal number; ρ is average density of overburden, kg/cm3; g is gravitational acceleration, m/s2; H is reservoir depth, m; ps is reservoir fluid pressure, MPa; and pwf is flowing bottomhole pressure during production, MPa

If Equation (1-21) is satisfied, that is, C≥σt, under the aforementioned producing pressure drawdown (ps – pwf), the borehole wall rock is firm and the structural failure of rock will not be caused, the rock matrix sand production will not be generated, then the sand control completion mode will not be selected. However, when the reservoir has low consolidation strength and the maximum tangential stress of borehole wall rock exceeds the compressive strength of rock, the structural failure of rock may be induced and the rock matrix sand production from the reservoir may be generated, then the sand control completion mode should be adopted

The meanings of the parameter signs are the same as described earlier. By comparing Equation (1-21) with Equation (1-22), it is shown that due to the Poisson's ratio of rock, which is generally between 0.15 and 0.4, (3 − 4υ)/(1 − υ) > 2υ(1 − υ). Then, at the same buried depth, the tangential stress borne by the borehole wall rock of a horizontal well will be higher than that of a vertical well. Therefore, at the same buried depth, for the formation, from which sand production will not be generated in a vertical well, sand production is still possible in a horizontal well. Similarly, the discriminant for determinating the firmness of borehole wall rock of a horizontal well is as follows:

The Mohr–Coulomb model describes a few material properties. The angle ϕ is defined as the angle of friction. Sandstone, for example, will exhibit friction along a shear plane as the grains will restrict motion. This is the case irrespective of the sand grains being cemented or not. The cohesive strength τo, on the other hand, reflects the degree of cementation of the material

Eq. (12.72) is identical to the solution for wellbore collapse, except for the boundary condition. For wellbore collapse, typically the wellbore pressure is higher than the pore pressure, requiring a nonpenetrating boundary condition. For underbalanced drilling and sand production, the wellbore pressure is equal to the pore pressure giving a penetrating boundary condition (see Section 12.7). The least principal stress then becomes

Sand production affects the pipeline design and operations mainly in three areas. One is that sands in the pipeline increase pipeline erosion. Another is that fluid velocity would have to be high enough to carry the sands out of the flowline. Otherwise the sands can deposit inside the pipeline and block the flow. Finally, sand deposition inside the pipeline can prevent inhibition chemicals, like corrosion chemicals, from touching the pipe wall, thus reducing the effectiveness of chemicals

The most challenging tasks of assessing the sand impacts on pipeline design are determining the particle sizes and determining the concentration of the sands that would be transported by the pipeline. Both particle size distribution and concentration depend upon such parameters as formation rock types and sand control technologies used in well completion. If the formation is unconsolidated, more sands can potentially be produced. Sand grain sizes can be determined by obtaining representative formation samples and performing sieve analysis (Bradley, 1987). Once grain sizes are determined, the proper sand control method can be designed to block the sand from flowing into wellbore and surface pipeline

Even the best sand-control technologies can potentially fail and allow sands to be introduced into the production system, including the pipeline. Thus, sand detection becomes very important for pipeline operations. No matter whether an intrusive technique, like impedance sensors, or a nonintrusive technique, like ultrasonic sensors, is used for sand detection, an accurate interpretation method must be developed

The Mohr-Coulomb model describes a few material properties. The angle φ is defined as the angle of friction. Sandstone, for example, will exhibit friction along a shear plane as the grains will restrict motion. This is the case irrespective of the sand grains being cemented or not. The cohesive strength τo, on the other hand, reflects the degree of cementation of the material

Equation 11.72 is identical to the solution for wellbore collapse, except for the boundary condition. Typically for wellbore collapse, the wellbore pressure is higher than the pore pressure, requiring a non-penetrating boundary condition. For underbalanced drilling and sand production the wellbore pressure is equal to the pore pressure giving a penetrating boundary condition (see Section 11.7). The least principal stress then becomes:

As Canadian oil sands production is set to enter a period of strong growth and expansion, a number of environmental issues and challenges are facing the industry. Most attention has been given to accelerating greenhouse gas emissions, but other environmental issues such as surface disturbance and water conservation also represent serious problems for the operators of oil sand projects and need to be weighed against the economic aspects of oil sand development (Charpentier et al., 2009; NEB, 2006; Swart and Weaver, 2012)

In the perspective of peak oil, Canada’s huge reserves of unconventional oil have the world’s attention. It is often claimed that nonconventional oil production such as oil sands production may bridge the coming gap between the world’s soaring oil demand and global oil supply

The world’s nonconventional oil initially in place could amount to as much as 7 trillion barrels (7×1012 bbl). Oil sand deposits in Canada and the United States as well as extra heavy oil in Venezuela account for the majority of these resources. However, the amount of bitumen (and, hence, synthetic crude oil) that could be recovered from these resources is very uncertain

The strong growth in oil demand indicates that Canada’s vast resources of oil sand may have a market. However, as the oil sand industry strives to exploit these resources, significant challenges must be overcome, most importantly higher natural gas prices, capital cost overruns, and environmental impacts

Critics contend that government and industry measures taken to minimize environmental and health risks posed by large-scale mining operations are inadequate, causing damage to the natural environment. In fact, there are those critics who would have oil sand development stopped—there appears to be concern that oil sand development rapes the environment and will leave it a disaster area for future generations. This is not quite the case

It has long been recognized that there is the need for responsible resource development, and the various levels of government have put the criteria in place to assure minimal environmental impact through (1) science-based precautionary limits that tell us when ecosystems are threatened and (2) improvement of the systems and approaches for monitoring and addressing the impacts of oil sand development on the climate, air, freshwater, boreal forest, and wildlife. In fact, the establishment and implementation of an effective oil sands monitoring is fundamental to the long-term environmental sustainability and economic viability of a rapidly growing oil sands industry in Canada (Dowdeswell et al., 2010) or, for that matter, in any country that seeks to follow development of indigenous oil sand resources

Characteristics of reservoir formations susceptible for deformation and sand production are reviewed. Stress-induced formation damage resulting from reservoir formation compaction, subsidence, and sanding processes is investigated. The mechanical and hydrodynamic processes causing sand production, migration, and retention in reservoir formations are described and modeled. Typical features of effective gravel pack designs are explained. The various parameters affecting the gravel-pack efficiency are discussed. The criteria available for effective selection of sand control techniques are reviewed. Predictive models for sand filtration and retention in gravel packs and applications by means of typical test data are presented

The operation of any piston pump is based on the relative movement between the piston and cylinder. From this follows that the same pumping action is achieved in a rod pump if the plunger is stationary and the barrel moves. The traveling-barrel rod pumps operate on this principle and have the plunger held in place while the barrel is moved by the rod string. The position of the anchor or hold-down is invariably at the bottom of the pump assembly

Traveling-barrel rod pumps are versatile and can be used in normal, sandy, and corrosive wells. Figure 3.8 gives a cross-section of an RHT pump. The plunger is attached to the bottom hold-down by a short hollow pull tube, through which well fluids enter the pump. The standing valve, situated on top of the plunger, is of a smaller size than the traveling valve. Thin-wall pumps are designated RWT and those with a soft-packed plunger RST

The traveling barrel keeps the fluid in motion around the hold-down, preventing sand or other solids from settling between the seating nipple and the hold-down. Therefore, pulling of the pump assembly is usually trouble-free

The size of the standing valve is limited because it has to fit into the barrel. This relatively smaller valve offers high resistance to fluid flow, allowing gas to break out of solution, causing poor pump operation in gassy wells

In deep wells, the high hydrostatic pressure acting on the standing valve on the downstroke may cause the pull tube to buckle and excessive wear can develop between the plunger and barrel. This limits the length of the barrel that can be used in deep wells

For an unconsolidated or weakly consolidated sandstone formation, sand production is the main obstacle affecting the normal production of oil and gas well. The sand control techniques normally used are divided into sand control without screen and sand control with screen. The former includes mainly fracture pack sand control, chemical sand consolidation, and perforating sand control, while the latter has a bottomhole mechanical sand control device including slotted liner, wire wrapped screen or prepacked screen, inside casing gravel pack, and openhole gravel pack

Perforating sand control means to ensure the long-term stability of perforation by the rational selection of perforating parameters and to avoid the risk of a large amount of sand production caused by the change of drawdown pressure, the depletion of reservoir pressure, and the increase of water cut on the premise of the minimum sand production rate that can be borne. Formation sand production is first due to perforation destabilization and failure, which lead to the falling-off of matrix sand and then due to the migration of sand. The failure of perforation is mainly caused by the change of the stress around perforation, which is generated by the change of drawdown pressure and the depletion of reservoir pressure. The migration of sand is generated by the flow velocity of fluid. The theoretical studies, numerical simulations, and laboratory and field studies indicate that the optimization of perforating parameters (mainly perforation penetration depth, perforation density and phase) is of great importance to achieving perforating sand control.a.Perforation penetration depth. The deep penetrating perforating charge should be selected as far as possible because, for the stability of single perforation, the deep penetrating charge has a greater perforation penetration depth and a smaller perforation diameter, so that the mechanical stability of perforation is much higher than that of the perforation generated by larger diameter charge.b.Phase and perforation density. In addition to the stability of single perforation, the effect of interactions between perforations on stability should also be considered; that is, the distances between perforations should be sufficient to avoid the mutual overlapping of the elastoplastic stress areas in the vicinity of perforations during oil and gas production and prevent the sloughing and failure of single perforation from leading to a chain reaction, thus avoiding the sloughing and sand production of the whole perforating section.Perforation spacing may be directly affected by perforation density and phase (Figure 6-59). The lower perforation density (that is, larger perforation spacing) has a smaller mutual interference between perforations; however, the flow rate of single perforation may be increased and the sand migration and production may be generated. Therefore, perforation density should be in a rational range, and the perforation spacing should be maximized by optimizing shot phasing.Sign in to download full-size imageFigure 6-59. Stretch view of perforation spacing under phase of 60°.In order to obtain the maximum perforation spacing, under a given wellbore diameter and perforation density, the optimum phase is under the condition of L1 = L2 = L3. However, it is impossible for the three to be equal when the perforations are spirally distributed. Thus the optimum phase is just the phase under which two of the three are equal. Their geometric relation is shown in Equations (6-45) through (6-48) (the SI unit system is used):(6-45){d1=1kmd2=π180∘×α×Rmin(6-46)L1=360∘α×d1(6-47)L2=L1+L3−2L1L3cosθθ=arctan(d2/d1)(6-48)L3d12+d22where: km = perforation density; α = phase angle (°); Rmin = minimum distance between the middle point of perforating gun and reservoir face (it is the wellbore radius when the perforating gun is centrical).Given Rmin and α, it follows that it can be achieved by optimizing perforation density.c.Oriented perforating. Under the condition of greater differences among vertical reservoir stress, maximum horizontal principal stress, and minimum horizontal principal stress, in order to increase the stability of perforation, oriented perforating should be adopted as far as possible, and the oriented azimuth should be consistent with the direction of the maximum principal stress (the deviation should not exceed 15–20°) [19].If oriented perforating cannot be achieved, the existing equipment also cannot be used for adjustment to meet the requirement of maximizing perforation spacing. The studies (by N. Morita et al. in 1989) indicate that under low perforation density the phase of 90° has higher critical pressure difference than the phase of 60°, while under high perforation density (>20 shots/m), the perforation stability under the phase of 60° is obviously higher than that of 90°, and the perforation stability may not be decreased even if the perforation density is increased to 40 shots/m (Figure 6-60).Sign in to download full-size imageFigure 6-60. Relation between the critical sand production pressure difference and perforation density and phase angle (Morita [3]).d.Perforating underbalance pressure. The perforating underbalance pressure should avoid perforation sloughing during cleaning perforation

Perforation penetration depth. The deep penetrating perforating charge should be selected as far as possible because, for the stability of single perforation, the deep penetrating charge has a greater perforation penetration depth and a smaller perforation diameter, so that the mechanical stability of perforation is much higher than that of the perforation generated by larger diameter charge

Phase and perforation density. In addition to the stability of single perforation, the effect of interactions between perforations on stability should also be considered; that is, the distances between perforations should be sufficient to avoid the mutual overlapping of the elastoplastic stress areas in the vicinity of perforations during oil and gas production and prevent the sloughing and failure of single perforation from leading to a chain reaction, thus avoiding the sloughing and sand production of the whole perforating section