RU2202034C2 - Procedure bringing well to optimum condition after repair - Google Patents

Abstract

FIELD: production of fluid fossils, oil and gas industry. SUBSTANCE: invention refers to operation of pumps installed in wells. Procedure includes placement of well pumping equipment at rational depth and pumping of fluid into oil collection system. Down-hole pumping equipment in which pump operates under cyclic condition and has capacity at which rated production is by far higher than maximum discharge of fluid before repair is installed during repair for periodic formation of hydrodynamic pulses. In this case pump is positioned at depth securing least specific expenses per ton of extracted well product under cyclic operation. Operation time of pump under cycle of regular operation conditions after repair is assumed to be equal to functional of boundary operation conditions of pump, time and rate of filling of hole clearance and is found by analytical expression. EFFECT: reduced negative effect of killing and optimized production after repair of well. 1 cl, 4 dwg, 1 tbl

Description

 The invention relates to the extraction of liquid minerals mainly in the oil industry and can be used in deep-pump operation, in particular, oil wells.

 There is a method of increasing (optimizing) oil recovery, including technological excerpts (Pat. RF 2156352, IPC 6 E 21 V 43/22, 2000).

 A known method of oil selection from wells using a deep pump, with the assessment of the parameters of the oil extraction system (Pat. RF 2011812, 6 E 21 In 47/00, 1990).

 The disadvantage of these methods is the impossibility of increasing the throughput capacity of deep-well pumping installations in the after-repair period.

 A known method of producing fluid using a deep-well pumping unit with a high-capacity pump and the possibility of periodic engine shutdown (Pat. RF 2061175, IPC 6 E 21 V 43/00, 1996).

 The disadvantage of this method is low flow rate at high cost.

 There is also a known method adopted for the closest analogue that a well can be brought to the optimum mode for fluid selection, which includes placing a downhole pumping device (equipment) located at a rational depth in the well and pumping fluid into the oil gathering system (RF Application 95108838, IPC 6 E 21 B 43/00, 1995).

 The disadvantage of this method is the inability to optimize production after repair by a set of indicators, significant time spent on reaching normal operation, including due to the negative effect of killing the well during repair.

 The technical task is to reduce the negative impact of well plugging and optimizing production in the after-repair period of the well according to a set of indicators by periodically creating hydrodynamic pulses, increasing the total obtained well production rate and increasing depression on the formation, increasing the fluid velocity inside the formation to increase well productivity, and increasing the throughput of the deep pumping units and reducing oil production costs while increasing gas-liquid throughput Mesi.

Figure 1 shows the dependence of the instantaneous flow rate of a well during stationary operation of the pump; figure 2. - time dependence of the instant flow rate of the well during cyclic operation of the pump; figure 3. - dependence on the time of accumulated production rate; figure 4. is an example of the energy characteristics of pumps, where 1 is the time dependence of the accumulated flow rate for the stationary mode, 2 is the time dependence of the accumulated flow rate for the cyclic mode, 3, 4 are the indicators H = f (Q), 5, 6 are the indicators η = f ( Q), 4, 6 - for stationary pumps, 3, 5 - for cyclic pumps, Q - nominal pump capacity, cm ³ / s, N - head, m, η - efficiency,%.

In contrast to the known solution in the method, well repair work is performed during well repair, which may include killing the well with saline solution, lifting of underground equipment, preventive maintenance during current repair or work on well overhaul, lowering downhole pumping equipment, launching the well, and normal operation of fluid production. During the repair, the downhole pumping equipment is installed with a pump capacity of P ₁ >> P ₂ , where P ₁ is the nominal capacity of the pump installed during the repair, P ₂ is the maximum fluid flow rate before the well is repaired; the pump is placed at a depth that provides the smallest unit cost per ton of produced well products, with the possibility of its operation in a cyclic mode with technological shutter speeds with regular fluid production. The pump run time in the cycle of the normal operation after repair can be taken based on the functionality of the boundary conditions of the pump, the time and speed of filling the annulus:
Т _pi = f (П ^У _i , t _{0 (i-1)} , V _{0 (i-1)} ),
where i> l is the sequence number of the cycle;
T _pi - pump run time in the i-th cycle, h;
P ^U _i - the boundary conditions of the pump in the i-th cycle, cm ³ / s;
t _{0 (i-1)} - time to fill the annulus in the (i-1) th cycle, h;
V _{0 (i-1)} is the annulus filling rate in the (i-1) th cycle, cm ³ / s;
boundary operating conditions of the pump П ^У _i - accept
P $\genfrac{}{}{0ex}{}{\text{Y}}{\text{i}}$ = f _i (φ _j , ψ _k ),
according to the functions of the energy characteristics of the pump:
H = f (Q),
where φ _j - filtration characteristics of the reservoir and the well,
ψ _k - technological modes of operation of the well, and
φ ₁ = (r _c ), φ ₂ = (χ), φ ₃ = (ε),
φ ₄ = (K _ol ), ψ ₁ = (ΔP), ψ ₂ = (Q),
where φ ₁ is the reduced radius of the well, cm;
φ ₂ - the coefficient of piezoelectricity of the reservoir, cm ² / s;
φ ₃ - reservoir hydraulic conductivity, μm ² • m / mPa • s;
ψ ₁ - downhole pressure drop during the pump operation, MPa;
ψ ₂ - nominal pump capacity, cm ³ / s;
i is the cycle number;
φ ₄ - well productivity coefficient, cm ³ / s • MPa;
N - pressure, m;
Q - nominal pump capacity, cm ³ / s;
the pump run time in the first cycle T _p1 can be set to a minimum and equal to 1.5-1.7 hours

 The method of bringing the well to the optimal mode of operation after repair includes techniques that reduce the negative effect of well killing, eliminate the dependence of actual production on the characteristics of underground equipment - eliminate errors in choosing underground equipment after repair. It is applicable due to the selected equipment and its operating mode for cleaning from drilling mud, industrial water and mechanical impurities, when the initial production rate drops due to clogging of the bottomhole zone of the well, for opening additional layers and increasing oil recovery, restoring the well operating mode and reducing water cut.

 The essence of the application of the method is to create an unsteady mode of operation of the well by means of forced selection during the period of operation of the well and its shutdown in the subsequent period. At the same time, the conditions for intensive impact on the formation and the well are created, leading to an increase in the productive performance of the well. They are the result of the removal of mud products, particulate matter, resins, paraffins, asphalts, as well as increasing the permeability of the formation, etc.

 The known method of steady well operation is due to the fact that the bottomhole pressure remains constant, the stress in the formation does not change, and the moving flow is not enough to clean the bottomhole zone. On the contrary, as practice shows, during operation, the well becomes clogged, production decreases until the well stops working.

 In contrast, the proposed method of well development provides an unsteady alternating impact on the formation, actively affecting the improvement of well productivity and increase production.

 One of the effects is associated with forced withdrawal of fluid from the reservoir. Forced selection leads to an increase in depression on the formation, the consequence of which is a continuous decrease in bottomhole pressure and a decrease in the dynamic level until the pump is received. In this regard, with forced selection, the well cannot work continuously. It is necessary to periodically shut off the well to restore bottomhole pressure.

 In this case, the following types of impact on the formation, contributing to the development of the well, reduce the negative impact of killing.

 These are alternating mechanical stresses in the formation during the period of forced selection and well shutdown. The number of changes in loading and unloading the formation can be 10-12 per day or about five hundred per month. Also, the effects are on the skeleton of the reservoir, which is not a continuous, but a discrete medium with a connection of mineral grains with thin weak bridges.

 The result of exposure to variable mechanical loads is both reversible and irreversible changes in the reservoir, which, in combination with changing filtration flows during operation and shutdown of the well, create favorable conditions for cleaning the bottom-hole zone.

 Under mechanical stresses in the reservoir, a periodic change in pore volume occurs - expansion and contraction. The same thing happens with the channels connecting them, as a result of which there is an additional possibility of removal of solid particles and highly viscous oil components. Along with the deformation of the pore space, there is a change in the cracks - their opening and closing. With each change of stresses, this process contributes to the formation of new cracks, which propagate deeper into the formation. This phenomenon is similar to hydraulic fracturing, but differs in that single large cracks are typical for hydraulic fracturing, and for this case, massive cracks.

 Variations in the formation contribute to an increase in permeability, hydraulic conductivity and piezoconductivity of the formation. Zones of improved filtration characteristics cover ever-increasing dimensions of the formation, contributing to an increase in the well productivity coefficient and a reduction in the cost of a ton of production.

 The method provides a reduction in the number of repairs (especially capital) associated with the intensification of the influx, restoration of potential and equalization of the oil recovery profile.

The cyclic mode of operation of the pump is ensured by the adopted pump capacity, much higher than expected well production (P ₁ >> P ₂ ) for more intensive inflow to the bottom and at the same time the possibility of creating a hydrodynamic impulse, while the fluid comes not only from the bottom but also from the annulus of the well and a section of the wellbore located below the pump.

 In FIG. Figure 1 shows the dependence of the instantaneous flow rate of a well for a widely used stationary mode with constant pump operation. The initial section (exit to the stationary mode) is followed by a constant flow rate during the entire pump operation. This mode corresponds to a straight line (figure 3, position 1) of the accumulated flow rate. In cyclic mode, there is a stepwise change in the flow rate corresponding to the cycles of the pump operation mode (Fig. 2). The accumulated flow rate (Fig. 3, pos. 2) reflects the stepwise nature of its change with inclined sections during the pump operation and horizontal platforms during the idle period. The accumulated flow rate of the cyclic mode exceeds the accumulated flow rate in the stationary mode (figure 3, position 1).

 The total obtained flow rate of the well exceeds the flow rate of the well during stationary operation of the pump for the following reasons.

 The use of a high-power pump has several effects on the reservoir. Depression into the reservoir increases, leading to intensification of the flow. In addition, an increase in the velocity inside the formation helps to clean the bottom-hole zone of the formation, to improve the filtration properties, to connect previously not working layers, which leads to an increase in the well productivity coefficient.

 The processes of changing the state of the reservoir extend even deeper into the reservoir and improve the filtration characteristics of the reservoir, such as the permeability and piezoconductivity coefficients of the reservoir, increase the mobility of a fluid, such as oil, hydraulic conductivity and others. They are caused by a change in the pore state of the formation, the opening of cracks, the appearance of additional micro- and macrocracks up to hydraulic fracturing, as well as manifestations of deforming properties, and are the result of exposure to increased pressure gradients and cyclic stress state.

 After turning off the pump during the idle time of the well, the flow of fluid from the reservoir to the bottom continues, filling the annulus. In addition, this ensures a reduction in energy consumption after switching off the pump.

 During production, for example, of oil, the following positive transformations of the liquid in the well occur during idle time: oil enrichment, oil purification from solid particles, removal of free gas from oil, and also the return flow of water from the well to flooded interlayers.

 The enrichment of oil is due to the process occurring in a stopped well, namely, that there is a flotation separation of water and oil, in which water drops down and oil floats up. As a result, enriched oil is accumulated in the borehole space under the pump, which is removed to the surface in the next cycle.

 On the other hand, the settling water again begins to penetrate into the reservoir. However, it does not enter all open intervals of the formation, but only to the maximum permeable ones, since there is less back pressure in them than in low-permeability layers.

 In highly permeable layers, water breaks through the fastest, therefore, they are the first to be flooded. As a result of this, the return flow of settling water from the well back to the reservoir improves the conditions of the hydrodynamic situation in the "reservoir - well" system. Purification of the fluid in the well from solid particles occurs under the influence of their different densities. In this case, solid particles that appear during the process of cleansing the reservoir, fall into the sump and do not interfere with the operation of the pump. They are removed only during well overhaul.

 An essential factor in the operation of the pump is the presence of free gas in the pumped liquid, which has a negative effect.

 In the idle mode of the well, the released free gas from the fluid flows through the annulus of the well. As a result of this, the amount of free gas under the pump decreases until it disappears completely, which is also a positive factor of the proposed method in comparison with the known method.

 The enrichment process, for example, oil, is also due to the composition of the liquid in the annulus, which is filled with almost pure oil, in contrast to watered oil flowing from the reservoir to the bottom, and when the pump is turned on, it is removed from the annulus to the surface.

 The operation of the pump in the cycle of normal operation consists of two components, one of which is connected with its inclusion for a period during which the boundary conditions of its operation are not achieved, and the other of which is associated with a shutdown.

 After reaching the boundary conditions, the pump is turned off, and in the well during the shutdown period, the flow of fluid from the reservoir continues, filling the annulus of the well.

With an arbitrary nature of changes in the properties of the reservoir and other parameters, the duration of the periods in the cycle of the standard operation mode is characterized by a universal dependence on the boundary conditions of the pump, the time and speed of filling the annulus in the form:
Т _pi = f (П ^У _i , t _{0 (i-1)} , V _{0 (i-1)} ), (1)
where i> 1 is the sequence number of the cycle;
T _pi - pump run time in the i-th cycle, h;
P ^U _i - the boundary conditions of the pump in the i-th cycle, cm ³ / s;
t _{0 (i-1)} - time to fill the annulus in the (i-1) th cycle, h;
V _{0 (i-1)} is the annulus filling rate in the (i-1) th cycle, cm ³ / s;
the boundary operating conditions of the pump П ^У _i - according to the functions of the energy characteristics of the pump
H = f (Q),
where N is the pressure, m;
Q - nominal pump capacity, cm ³ / s;
the pump run time in the first cycle T _p1 is set to a minimum and equal to 1.5-1.7 hours

 This ensures that the pump can operate in a cyclic mode of regular fluid production and carry out this production in accordance with the obtained parameters.

где q_cp - среднесуточный дебит скважин, м³/cyт;
q_max - дебит во время работы насоса, м³/сут;
t_p - время работы насоса в цикле, ч;
t_ocт - время останова насоса в цикле, ч.Given the idle time t _{oct the} total flow rate for one cycle will be

where q _cp is the average daily flow rate of wells, m ³ / cyt;
q _max - flow rate during pump operation, m ³ / day;
t _p - pump operating time in the cycle, h;
t _oct - pump shutdown time in the cycle, h

The average flow rate q _cp depends, in particular, on the duration t _oct spent on filling the annulus.

The more t _oct , the higher the liquid level rises in the annulus. This leads to an increase in q _max with increasing idle time t _oct . In turn, the idle time has an effect on the average flow rate q _cp , determined by the formula. The result of an increase in qmax is shown in FIG. 3 with a higher position of the accumulated flow rate (2) in comparison with (1). In this case, such a duration t _{oct is determined} that leads to a larger average flow rate q _cp .

 Saving energy costs is due to three circumstances.

 The first of them is associated with the lack of energy consumption when the pump is turned off and idle. The second is due to the continued flow of oil from the reservoir in the absence of a working pump. The third circumstance is associated with the intensification of the inflow from the formation into the well due to the use of a high-power pump with an improvement in the reservoir properties of the formation and the bottom-hole zone towards their improvement.

Well 1116 was chosen for the development application due to the fact that during the previous time of its operation, a decrease in the well productivity coefficient was observed, leading to lower production rates with blockage of the bottomhole zone, which at the time of treatment was 9.3 m ³ / day.

At the Zapadno-Surgutskoye field, well 1116 in well 82 is developing a formation with a thickness of h = 16 m with the following reservoir properties: permeability coefficient of a formation k = 0.52 μm ² , piezoconductivity χ = 10 ⁴ cm ² / s, fluid viscosity μ = 3.5 MPa • s, fluid density in reservoir conditions γ = 0.77 t / m ³ .

The well was cased with a column of diameter R _k = 5 '', tubing pipes r _tubing = 2.5 '' were lowered into the column. Before applying the method, well 1116 belonged to a mechanized fund and was equipped with an ESP-30-1200 pump. At the same time, the pump was lowered to a depth of 1600 m and worked with a dynamic level of 1200 m. The fluid flow rate before applying the method was 9.3 m ³ / day with a water cut of 7%. The reduced well radius r _c = 8.5 cm.

 At this well, the proposed method is used to optimize production by a set of indicators, such as an increase in flow rate, a decrease in water cut, an increase in depression, etc.

For the implementation of the method, an ETsN-50-1700 pump is used. Its nominal productivity P ₁ = 50 m ³ / cyt significantly exceeds the expected fluid flow rate P ₂ = 9.3 m ³ / day, taken as a result of a previous well operation.

This ratio P ₁ >> P ₂ with an excess of more than 5 times provides the condition for the execution of the method.

 For the technical implementation of the method, the old pump is raised to the surface and the descent depth of the new ETsN-50-1700 pump is determined. To do this, choose a rational depth for a given size, which is 1740 m, and lower the pump to this depth.

Provide the ability to work in a cyclic mode of regular fluid production. For this, in this example, the condition for shutting down the working pump on the i-th cycle is set by the moment of reaching the level in the annulus N _{cr (i) of} 1600 m, which is 140 m higher than the depth of the pump descent. Further lowering may result in an accident.

The pump stop time is assigned for this cycle equal to t _{0 (i)} = 2 hours and is carried out, for example, by a timer.

For the conditions of an example implementation, the pump is turned on, the pump is automatically turned off when the fluid level in the annulus drops to a critical level of N _{cr (i)} , the pump is held for a timer over time, which enables the pump to operate in the cyclic mode of regular fluid production .

According to the results of applying the method to well 1116 of the West Surgut field, the following positive results were obtained. The fluid flow rate in the cyclic mode of regular fluid production increased to 21 m ³ / day, instead of the initial 9.3 m ³ / day, which corresponds to a 2.26-fold increase. There was a decrease in water cut to 3% instead of the previous 7%, i.e. 2.3 times. The average dynamic level became equal to 1100 m instead of the previous 1200 m, as a result of which the decrease in depression on the formation was equal to U = (1740-1100) / (1600-1200) = 1.6.

 The results obtained confirm the optimization of oil production as a result of applying the method according to the following indicators.

 Additional fluid production increased 2.26 times while reducing depression 1.6 times. The decrease in water cut was 2.3 times.

 Thus, the application of the method ensures the implementation of the goal: optimization of fluid production according to the specified set of indicators.

 The initial data determine the parameters of the cyclic process for two other wells 439 and 1162 (see table).

Thus, as a result of well development by the proposed method, an increase in the following filtration characteristics was obtained for wells 439 and 1162, respectively: reduced well radius φ ₁ from 0.02 to 0.1 cm and from 10.2 to 11.8 cm, piezoelectric conductivity coefficient φ ₂ s 3.0 • 10 ⁴ to 4.0 • 104 cm ² / s and s 2.0 • 10 ⁴ to 3.0 • 10 ⁴ cm ² / s, hydro conductivity φ ₃ from 52 to 65 and from 65 to 75 μm ² • cm / mPa • s), well productivity coefficient from 3.1 to 3.8 and from 2.3 to 2.8 m ³ / (Sut • mPa).

Claims (2)

1. A method of bringing a well to the optimum mode of producing well fluid, including placing downhole pumping equipment in the well at a reasonable depth and pumping fluid into the oil recovery system, characterized in that for the periodic creation of hydrodynamic impulses, downhole pumping equipment is installed when repairing the well with the possibility pump operation in cyclic mode with pump power
P ₁ >> P ₂ ,
where P ₁ is the nominal capacity of the pump installed during the repair;
P ₂ - the maximum flow rate before the repair of the well,
the pump is placed at a depth that ensures the smallest unit cost per ton of produced well products during cyclic operation, the pump runtime in the cycle of the normal operation after repair is equal to the functional of the boundary conditions of the pump, time and annular filling rate:
T _pi = f (P _i ^Y , t _{0 (i-1)} , V _{0 (i-1)} ),
where i is the sequence number of the cycle (i>l);
T _pi - pump run time in the i-th cycle, h;
P _i ^U - the boundary operating conditions of the pump in the i-th cycle, cm ³ / s;
t _{0 (i-1)} - time to fill the annulus in the (i-1) th cycle, h;
V _{0 (i-1)} is the annular space filling rate in the (i-1) th cycle, cm ³ / s,
the boundary operating conditions of the pump П _i ^У are taken equal
P $\genfrac{}{}{0ex}{}{\text{Y}}{\text{i}}$ = f _i (φ _j , ψ _k ),
where φ _j - reservoir characteristics of the reservoir and the well;
ψ _k - technological modes of operation of the well,
moreover:
φ ₁ - reduced radius of the well, φ ₁ = (r _c ), cm;
φ ₂ - piezoelectric conductivity coefficient of the formation, φ ₂ = (χ), cm ² / s;
φ ₃ - reservoir hydraulic conductivity, φ ₃ = (ε), μm ² • m / mPa • s;
φ ₄ - well productivity coefficient, φ ₄ = (K _ol ), cm ³ / s • MPa;
ψ ₁ - downhole pressure drop during the pump operation period, ψ ₁ = (ΔP), MPa;
ψ ₂ - nominal pump capacity ψ ₂ = (Q), cm ³ / s,
according to the functions of the energy characteristics of the pump:
H = f (Q),
where N is the pressure, m;
Q - nominal pump capacity, cm ³ / s,
the pump run time in the first cycle T _{p1 is} assigned a minimum and equal to 1.5-1.7 hours  2. The method according to claim 1, characterized in that during the repair they perform killing of the well with saline, carry out the lifting of underground equipment, perform preventive maintenance during the current repair or overhaul of the well, lower the pumping equipment, launch the well and carry out regular operation fluid production.

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