CN104704197A - SAGD control in leaky reservoirs - Google Patents

Abstract

The use of a water recycle ratio for controlling at least one Steam Assisted Gravity Drainage (SAGD) parameter in a leaky bitumen reservoir. Further, a process to control a steam injection rate for an individual SAGD well pair, in a leaky bitumen reservoir wherein the process replaces a pressure control for an SAGD steam injection rate with a volume control determined by a Water Recycle Ratio (WRR).

Description

SAGD in seepage reservoir controls

Background technology

SAGD (SAGD) improves oil recovery (EOR) method for the leading original position heating power of pitch of gathering in the oil-sand from Alberta province (Alberta) at present.This oil-sand is that hydro carbons the biggest in the world one of deposits.SAGD has the parallel water horizontal well that about 5 meters two of being separated by the vertical plane are about most 1000 meters long.The steam injection well of top controls by injecting steam rate, to obtain the goal pressure (i.e. " Stress control ") set by operating personnel.The pitch of below and water recovery well are controlled by pump rate (or other method), to maintain the fluid temperature (F.T.) (crossing cold or Automatic steam trap Trap control) lower than saturated vapour, guarantee do not have live steam to penetrate into described well.

When including vaporium, even if goal pressure is higher than natural reservoir pressure, above-mentioned control method is also effective.But quite a few resource of described oil-sand is damaged by pool (the poor district of top layer water, bottom water, distribution).Have a large amount of water to flow into or flow out, these can cause reservoir " seepage ".In these cases, SAGD is not effective to the Stress control of steam injection.Barometric gradient only needs appropriateness to carry the water of large volume and to destroy SAGD.Be difficult to select suitable pressure target or accurately measure suitable pressure to minimize the adverse effect to seepage reservoir.The invention describes a kind of substituted volume control method for carrying out SAGD steam injection to seepage reservoir.This technology comprises use WRR (water circulation ratio) as crucial measurement and controling parameters.WRR is the water produced and the volume ratio (by water gaging) injecting steam.

The pitch resource that Transport Model for Alberta economizes Athabasca is that hydro carbons maximum in the world one of deposits.As mentioned above, quite a few of this resource can be damaged by pool and cause reservoir " seepage ".In addition, Transport Model for Alberta economize Athabasca pitch resource due to following reason be unique:

(1) resource that Alberta is economized comprises about 2.75 trillion barrels of pitches (Butler, R. " ThermalRecovery of Oil and Bitumen ", Prentice-Hall, 1991), comprises carbonate sediment.This is one of maximum in the world liquid hydrocarbon resource.Resource of can gathering (not comprising carbonate sediment) is estimated to have an appointment 1,700 hundred million barrels at present---the mineral reserve (34,000,000,000 barrels) of 20% and original position EOR (1,360 hundred million barrels) (CAPP of 80%, " The Facts on Oil Sands ", in November, 2010).The estimator of described original position EOR is based on SAGD or similar technique.

(2) traditional oily reservoir has top seal (rimrock), and it prevents oil from leaking and comprising resource.Pitch by being fixing stage and being formed compared with lightweight oil sources through bacterial degradation to the pitch of wherein degrading under reservoir conditions.Bitumen reservoir can be generally self-packing (without rimrock sealing).If original position EOR technique touches top layer, then may not comprise this technique, and pitch may easily by the water above pitch or gaseous contamination.

(3) density of pitch is close to the density of water or salt solution.The density ratio water of some pitches is larger, and the density ratio water of some is less.At bacterial degradation and shape asphaltogenic period, the density of hydrocarbon can experience density transition, and water can be first little than the density of reservoir " oil ".The pool of bitumen reservoir to be arranged in above pitch (bottom water) below (top layer water), pitch or to be dispersed in the clean oil-producing area (the poor district of water (WLZ)) of pitch.

(4) most of pitch is formed at river or estuarine environment.For reservoir damages, this has two kinds of consequences.First, a large amount of reservoir inhomogeneities will be had.The second, the scale of described inhomogeneity be likely less than SAGD gather well pattern scale (Fig. 1) or be less than about 1000m dimensionally.Expection " on average " SAGD EOR technique will run into several inhomogeneity in each gathers well pattern.

SAGD is a fragile technique.Temperature and pressure is limited to the character of saturated vapour.Gravity drainage is by the pressure differential being low to moderate 25psia.Low temperature (in saturated vapour technique) and sub pressure gradient make SAGD technique easily be subject to as mentioned above due to the damage of reservoir inhomogeneity.

The invention describes a kind of substituted volume control method for carrying out SAGD steam injection to seepage reservoir.This technology comprises use WRR (water circulation ratio) as crucial measurement and controling parameters.WRR is the water produced and the volume ratio (by water gaging) injecting steam.

Summary of the invention

Following initialism will be used herein.

AOGR	American petroleum natural gas reporter reports
		CAPP	Petroleum Production ACSA of Canada
CMG	Microcomputer modelling group (Calgary)

CSS	Cyclic steam encourages
		EOR	Improve oil recovery
ETOR	Thermal energy oil ratio (MMBTU/ bucket)
		ESP	Electric submersible pump
GD	Gravity drainage (room)
		JCPT	Canada's petroleum technology magazine
LZ	Poor district
		P	Pressure
SAGD	SAGD
		SOR	Vapor oil ratio
SPE	Petroleum Engineer association
		T	Temperature
WLZ	The poor district of water
		WRR	Water circulation ratio

According to an aspect of the present invention, use water circulation ratio is provided for controlling at least one SAGD parameter in seepage bitumen reservoir.In one embodiment, described parameter is selected from volumetric rate, pressure, temperature and its combination.

According to another aspect of the present invention, provide the method controlling the SAGD steam injection speed that single SAGD well is right in seepage bitumen reservoir, described method comprises SAGD steam injection speed described in Stress control is replaced with fixing fabric structure.

Preferably, described seepage bitumen reservoir is determined by the geological knowledge of the WLZ, top layer water or the bottom water that scatter in SAGD well pattern volume; More preferably, described seepage bitumen reservoir is determined by the cold water injection test before starting at SAGD; Most preferably, described reservoir when utilize in 200 or more skies the SAGD of Stress control steam injection operate after measure WRR time and the change of WRR from 1.0 be greater than 10% time, be considered to seepage.

Preferably, described method comprised cold control (Automatic steam trap Trap control) liquid extraction (pitch+water) further.

In one embodiment, described volumetric rate controls to realize by being injected into well by the steam injection SAGD of default target volume speed.

In another embodiment, described volumetric rate controls to be realized by following step:

I. the WRR that continuous measurement SAGD well is right;

Ii. the target of WRR is established; With

If iii. actual WRR is less than target WRR, then reduce steam injection speed until obtain WRR target; Or

If iv. actual WRR is greater than target WRR, then increase steam injection speed until obtain WRR target.

Preferably, for the reservoir of intimate homogeneous, described target WRR is between 0.9 and 1.0.

Preferably, described method to be applied in pitch oil-producing area or near the seepage reservoir with height water saturation district, wherein target WRR is set between 1.0 and 1.5.

In one embodiment, described seepage reservoir is caused by the poor district of the water scattered in clean oil-producing area (WLZ).

In another embodiment, described seepage reservoir is caused by top layer pool.

And in another embodiment, described seepage reservoir is caused by bottom pool.

In another embodiment, described seepage reservoir is caused by the many factors comprising WLZ, top layer water and/or bottom water.

Preferably, described pitch is API density <10 and the hydrocarbon of viscosity >100,000cp under natural reservoirs condition.

In one embodiment, for loose (unconsolidated) reservoir, SAGD pressure in reservoir is no more than reservoir separating pressure (parting pressure), or for cementing (consolidated) reservoir, the SAGD pressure in reservoir is no more than reservoir fracture pressure (fracturing pressure).

Preferably, the maximum SAGD pressure of permission is about 80% of described separating pressure and/or described fracture pressure.

In another embodiment, minimum SAGD operating pressure equals natural reservoir pressure.

In one embodiment, described reservoir is positioned at the Athabasca area that Transport Model for Alberta is economized.

Accompanying drawing explanation

Fig. 1 describes the structure of typical SAGD well

Fig. 2 describes the stage of SAGD

Fig. 3 describes saturated vapour character

Fig. 4 describes pitch and heavy oil viscosity

Fig. 5 describes each well SAGD productivity ratio

Fig. 6 describes the waterpower limit of SAGD

Fig. 7 describes the poor district of pitch of distribution

Fig. 8 describes top layer water/bottom water: oil-sand

Fig. 9 describes SAGD simulation

Figure 10 describes the WRR performance of the homogeneous reservoir with the SAGD GD room (single well to) included

Figure 11 describes pitch void content and vapour volume

Figure 12 describes well to cross-flow model

Figure 13 describes the SAGD performance of case 1

Figure 14 describes the SAGD performance of case 2

Figure 15 describes the SAGD performance of case 2 (a)

Figure 16 describes the SAGD performance of case 3

Figure 17 describes the SAGD performance of case 4

Figure 18 describes the SAGD performance of case 5

Figure 19 describes the SAGD accumulation well of case 1-3 to performance

Figure 20 describes the SAGD accumulation well of case 1,4 and 5 to performance

Figure 21 describes the right output/performance of the dual well of SAGD of base case and case 2

Figure 22 describes the right SAGD Stress control performance of connected well

Figure 23 describes the right SAGD WRR performance of the connected well of case 3

Figure 24 describes the case 1 SAGD WRR performance right with the well that is connected of 3

Figure 25 describes the right bituminous production of the single well of case 3

Figure 26 describes the right pitch productive rate of two wells of base case and case 3

Figure 27 describes the SOR performance of base case and case 3

Detailed description of the invention

SAGD is a kind of pitch EOR method using saturated vapour energy to be delivered to bitumen reservoir.Fig. 1 shows basic SAGD geometry, and bottom pitch district, (bottom 8) top uses paired, the parallel horizontal well (2,4) (at most about 1000 meters long) of about 2 to 8 meters of being separated by.Saturated vapour injects in reservoir by the well (2) of top in same perpendicular.Described Steam Heating pitch and reservoir matrix.When interface between steam and cold pitch outwards moves up, form gas phase gravity drainage room (Fig. 2).The pitch of heating and the steam of condensation under gravity draining extremely produce the lower horizontal well (4) of liquid.The liquid (pitch+water) of heating uses ESP pump or gas lift system pumping (or transport) to ground.

It is how ripe that Fig. 2 demonstrates SAGD.Initial stage vaporium (1) is from steep sides and the top draining pitch from room.Increase (2) when described room and when touching the top of clean oil-producing area, stop from the draining at top, room, and when described room continues outwards to increase, the gradient of sidewall reduces.Asphalt production rate reaches peak value about 1000 barrels/day when described room touches the top of clean oil-producing area, and reduces (3) when described room outwards increases, until final (10-20) reaches limit economically.

Because extraction fluid has or close to the temperature of saturated vapour, the latent heat of described steam is therefore only had to contribute to described (in reservoir) technique.Guarantee that having high-quality when steam is injected in reservoir is important.

The feature of the SAGD technique in good, homogeneous reservoir can only be several measuring:

(1) temperature (or pressure) of saturated vapour

(2) asphalt production speed (crucial economic factor), and

(3) the measuring of SOR – process efficiency

For impaired reservoir, increase the 4th Liang Du – water circulation ratio (WRR).WRR makes it possible to understand that how many steam injected returns as condensed water.

In the second best in quality reservoir, the operation of SAGD is directly simple.The pressure target that the speed of steam injection upper water horizontal well and steam pressure are selected by operator controls.If pressure is lower than described target, then improve steam pressure and charge velocity.If pressure is higher than described target, then carry out contrary operation.Control the throughput rate of lower horizontal well to realize cold target in the extraction fluid of average temperature.Crossing cold is difference between the temperature of saturated vapour and the actual temperature of extraction fluid (pitch+water).Under extraction fluid remains on the temperature lower than saturated vapour, to guarantee that live steam is not plucked out of.20 DEG C is typically cross cold target.This is also referred to as Automatic steam trap Trap and controls.

The operator of SAGD has two kinds of selections---the cold target of mistake of technique and operating pressure.Crossing cold is safe option, but operating pressure is meticulousr, usually even more important.Pressure is higher, the temperature be associated with the character of saturated vapour higher (Fig. 3).Along with operating temperature raises, the temperature of the pitch of heating also raises, and it reduces the viscosity of pitch conversely.The viscosity of pitch is the majorant (Fig. 4) of temperature.The right productivity ratio of SAGD well is proportional to the square root (Butler (1991)) of asphalt viscosity inverse.So pressure is higher, gathering of pitch is faster---a crucial economic performance index.

But, if pressure increase, can efficiency be lost.The latent heat of steam is only had to contribute to (in reservoir) SAGD technique.When vapor pressure enhancement and temperature are to improve productivity ratio, the latent heat content of steam declines (Fig. 3).In addition, when raised pressure and temperature, need more multi-energy that reservoir matrix is heated to saturated-steam temperature, and heat waste increase (SOR and ETOR increase).

SAGD operator selects to maximize economic well-being of workers and staff, therefore operator's raised pressure and temperature as much as possible usually.Pressure is usually much higher than natural reservoir pressure.Certain operations person has operated excessively, has exceeded separating pressure (fracture pressure), and cause the surface of steam and sand penetrate (Roche, P. " Beyond Steam ", New.Tech.Mag., in September, 2011).For best reservoir, the peak value of asphalt production rate is about 1000 barrels/day, but for poor reservoir, asphalt production rate can significantly impaired (Figure 27).

Also may there is waterpower limit (Fig. 6) in SAGD.Hydrostatic head between two SAGD wells (2,4) is about 8psia (56kPa).When pump inhale or extraction pitch and water (12) time, there is nature pressure drop due to frictional force in described well.If this pressure drop exceedes described hydrostatic head, then vapor/liquid interface may " inclinations " crossing with recovery well or Injection Well (2,4).If crossing with recovery well (4), then steam may penetrate.If crossing with Injection Well (2), then its possibility overflow, and effective Injection Well length may be shortened.For the spacing of 5m between current standard pipe sizes and well (2,4), the length of SAGD well is limited to about 1000 meters.

Common remedying for the impaired SAGD reservoir with water invasion is that the operating pressure of SAGD is reduced to " coupling " natural reservoir pressure---also referred to as low pressure SAGD.It is due to following reason, and this is difficult under best-case, and is unpractical in the worst cases:

(1) there is natural static pressure gradient in clean oil-producing area.Such as, for the clean oil-producing area of 30m, hydrostatic head is about 50psi (335kPa).Because vaporium is gas, its place under a constant.What pressure should be selected to mate reservoir pressure?

(2) also there is side pressure gradient in SAGD.Select the pipe size of SAGD recovery well, so that the natural pressure gradient when pump is inhaled is less than the differential static pressure (about 8psi or 56kPa) between SAGD steam injection well and pitch recovery well.Do you if there is side pressure gradient, how SAGD pressure and reservoir pressure can be matched?

(3) be difficult to the Stress control of SAGD, and to measure be coarse.Expection having the ± Stress control uncertainty of 200kPa.

When containing vaporium, even if goal pressure is higher than natural reservoir pressure, control method above is also effective.

As mentioned above, described oil-sand has quite a few resource and is damaged by the poor district of water (the poor district of top layer water, bottom water, distribution).When flowing into when there being a large amount of water or flow out, these can cause reservoir " seepage ".Under these conditions, not effective to the Stress control of the SAGD of steam injection.Barometric gradient only needs appropriateness to carry the water of large volume and to destroy SAGD.Be difficult to select suitable pressure target or accurately measure suitable pressure to minimize the adverse effect to seepage reservoir.

The poor district of water (WLZ)

The poor district of water (WLZ) with high water saturation at the top layer of bitumen reservoir (top layer water), bottom (bottom water), or can be dispersed in oil-producing area.

Fig. 7 describes the WLZ18 of distribution.When faced with this situation, can observe following:

I. the WLZ scattered must heat, this district can be encapsulated to make GD vaporium and GD room can continue to rise to WLZ block on or around.

Ii.WLZ has the thermal capacitance higher than pitch oil-producing area.Following table 3 shows WLZ to be increased compared to 25% thermal capacitance of oil-producing area.

Iii.WLZ also has the thermal conductivity higher than pitch oil-producing area.Such as, WLZ has the thermal conductivity (table 2) being greater than pitch oil-producing area twice.

Iv. therefore, even if described WLZ is not by aquifer or the supply of bottom/top layers water, WLZ also will when vaporium passes it through heat loss (thermal penalty).In addition, because WLZ has few pitch, asphalt production rate also will at vaporium through impaired during WLZ.

The water of WLZ can be heated to saturated-steam temperature or close to saturated-steam temperature by v.SAGD steam, but it can not evaporate the water of WLZ.WLZ's breaks needs water as fluid discharge.

If the WLZ vi. scattered serves as leakage district, then described problem is the most serious.The bootable steam of WLZ leaves SAGD vaporium.If the condensation before removal of described steam, then have lost water, but can retain heat.If but described steam left GD vaporium before condensation, then described technique is by both loses heat and water.

Vii. significantly remedial measure is that the pressure of reduction SAGD is to minimize the overflow of steam or water.If but carrying out this remedies, then asphalt production rate will reduce.

If if viii. pressure drop too much or local pressure too low, then the cold water of missing district from WLZ may flow in GD vaporium or flow to SAGD recovery well.If there occurs these, then the generation of water may exceed steam injection.The more important thing is, for large inflow, the Automatic steam trap Trap that have lost as SAGD control method controls (crossing cold control).

Ix. the WLZ scattered can the shape of distortion SAGD vaporium, if particularly the lateral dimensions of WLZ is limited.Normal growth slows down when WLZ breaks.This will reduce productivity ratio, lower efficiency and limit recovery ratio.

For bottom pool 20, as high-visible in Fig. 8, question marks are similar to the WLZ of distribution, and difference is 1) bottom water is in the below and 2 of the clean oil-producing formation of pitch) expection bottom water has more activity.As long as situation below exists, SAGD just can operate under the pressure being greater than reservoir pressure: pressure drop 1) in recovery well (because flowing/pump is inhaled) does not make local pressure be down under reservoir pressure, and 2) bottom reservoir below recovery well by full-bodied firm pitch (substrate pitch) " sealing ".When described technical maturity, substrate pitch is heated by the conduction from recovery well.After several years, this pitch will become piecemeal activity, and needs reduce to mate reservoir pressure by SAGD pressure.This can be fragile balance.SAGD pressure can not be too high, otherwise can form passage (reverse bore into) to allow the UNICOM with bottom water.SAGD steam pressure can not be too low, otherwise water will sucking-off from bottom water (ridge enters).If there occurs this situation, then the generation of water will exceed steam injection.Pressure drop in recovery well is higher, and described balance is more fragile, and it is more difficult to average out.

If if reservoir is inhomogeneous or heating mode is inhomogeneous, then passage or ridge enter can be part, and the generation of acceleration problem.

For top layer water 22 (as high-visible in Fig. 8), again, question marks are similar to WLZ and the bottom water of distribution, expect that top layer water is also active water supply.Question marks are similar to bottom water as above, and difference is SAGD well top layer water further away from each other.Therefore initial period (when described technique can operate under the pressure higher than reservoir pressure) can extend compared to bottom water.Pressure drop in recovery well is less important, because it is away from top layer.Primary problem may be that steam makes top layer water termination break.If top layer water is active, then water will overflow described room and can close described SAGD technique.

For WLZ, industrial have following empirical:

Respectively the control oneself WLZ that reports distribution of the Firebag SAGD project of i.Suncor and the Long Lake project of Nexen can play the effect of leakage district when SAGD hypertonia, force SAGD pressure (the Triangle Three Engineering that operator's Selection radio desired value is lower, " TechnicalAudit report; Gas Over Bitumen Technical Solutions ", in December, 2010).

Ii. the water invasion from SAGD bottom water also can cause more well-repairing work (i.e. downtime) (Jorshari due to unbalance steam and lift (lift) problem, K. " TechnologySummary ", JCPT, in March, 2011).

Iii. the analog study of concrete reservoir is concluded, the exploitation that the standoff distance (standoff) of 3m (be 3m from SAGD recovery well to the interface of pitch/water) is enough to make to have bottom water is best, the control of 1m is allowed to be used for drilling well accuracy (Akram, F. " Reservoir Simulation OptimizesSAGD ", American O & G Reporter, in September, 2010).In order to get core/earthquake resistant control, allow described standoff distance can be longer.

The WLZ that iv.Nexen and OPTI has reported distribution seriously hinders the SAGD asphalt production at Alberta province Long Lake and SOR is increased above initial expection (Vanderklippe, N. " Long Lake Project hits Sticky Patch ", Globe & Mail, on February 10th, 2011), (Bouchard, J. etc., " Scratching below the Surface Issuesat Long Lake-Part 2 ", Raymond James, on February 11st, 2011), (NexenInc. " Second Quarter Results ", press release, on August 4th, 2011), (Haggett, J etc., " Update 3-Long Lake oilsands output may lag targets ", Reuters, on February 10th, 2011).

V. the poor district having been reported Long Lake accounts for 3% to 5% (v/v) of reservoir (Vanderklippe (2011)), Nexen Inc (2011)).

Vi.Oilsands Quest reports the bitumen reservoir in poor district, the top with " being thinned to appropriateness ".Some regions have " poor district, the top that continuous print is thick ".(Oilsands Quest, " ManagementPresentation ", in January, 2011).

The oil sands projects that vii.Johnson reports Connacher has the poor district of pitch water, top.It is reported, described poor district is different from aquifer in two---" poor district is not filled with and size is limited " (Johnson, M.D. etc., " Production Optimization at Connacher'sPod One (Great Divide) Oil Sands Project ", SPE 145091-MS, 2011).

Viii.Thimm reports the peaceful river project (Peace River Project) of shell (Shell), and it comprises " basic poor pitch district ".The data analysis of cyclic steam stimulation process (CSS) is demonstrated to the character (that is, the quality in described poor district is key factor) be associated with the geology in poor district.The selected technology utilization character of WLZ, steam injection ability (Thimm, H.F. etc., " A Statistical Analysis of the Early Peace River ThermalProject Performance " that particularly WLZ is good, JCPT, in January, 1993).

Ix. the test of cold water injectability detects a kind of method (Aherne that SAGD well is connected with between WLZ, top layer water and/or bottom water potentially, A.L.et al., " Fluid Movement inthe SAGD Process:A Review of the Dover Project ", Can.Int'l Pet.Conf., on June 13rd, 2006).

The usual method that SAGD operation controls homogeneous reservoir first selects to exceed the operating pressure of natural reservoir pressure, to attempt to maximize asphalt production rate.Then, using selected pressure as target, steam regulation charge velocity and pressure are to reach goal pressure (Stress control).Based on the reason discussed in earlier paragraphs, if WLZ is destroyed, then normal operation sequence becomes difficulty.

The present invention includes improvement, preferably optimization SAGD is the method for the performance in " seepage " reservoir at WLZ reservoir (comprising the case of top layer water and bottom water) or wherein said reservoir." seepage " reservoir loses when operating pressure > natural reservoir pressure and injects fluid, or has fluid invasion when operating pressure < natural reservoir pressure.The present invention also comprises the water circulation ratio (WRR) of the reservoir measured containing WLZ district.WRR is the volume ratio of the water/injection steam produced, and wherein steam injection is measured as liquid-water equivalent.Different from Stress control steam injection speed, answer steam regulation to inject to make each SAGD well reach WRR target.

Embodiment 1

According to main imagination below, homogeneous SAGD EOR technique (single well to) is simulated:

(1) EXOTHERM ^tMsAGD mathematical model

(2) without the homogeneous Athabasca reservoir that reservoir damages

(3) universal property of pitch

(4) 25 meters of clean oil-producing formations

(5) 800 meters of SAGD wells, span (spacing) 100 meters, interval (separation) 5 meters

(6) 10 DEG C of mistakes are colod-application to be controlled in extraction

(7) 3MPa pressure is for injecting control

(8) use within 4 months of vapor recycle, start the cycle

(9) the well model of discretization, illustrates borehole pressure gradient.

Fig. 9 shows the performance of expection.Can see, the steam injection speed of expection reaches peak value at 2936 barrels/day, and asphalt production speed reaches peak value at 1002 barrels/day.Figure 10 shows the WRR performance of expection.Initial WRR is about 0.9,1200 days (3 ¹/ ₄year) after be increased to gradually and be greater than 0.99.

Although do not want, by this constraint, to should be understood that the heterogeneous reservoir for including, exist WRR will close to can not more than 1.0 two reasons of (except for short effusion (excursion)), that is:

(1) some pitch spaces produced are occupied by steam and form steam GD room.Suppose that these spaces are saturated steam and replace, Figure 11 this show the percentage of the injection steam occupying pitch space.Depend on pressure and SOR, steam can with 0.2 to 0.5% loss to recycling.If this is unique factor, then should expect that WRR trend is inject steam 99.5 to 99.8%.

(2) some pitch spaces produced will be occupied by aqueous water, particularly near the edge and/or heat loss area of steam GD room (that is, near top).Expect that this is main when starting close to SAGD technique, and reduce when steam stores and gathers.

(3) at the end of SAGD method is contiguous, bituminous production is low, and SOR increases fast.Great majority inject steam and are used to compensate heat waste.Seldom or do not have pitch space to produce and steam/water " short circuit ".Again, this be WRR close to 1.0 reason.

How Figure 10 will be SAGD work if being presented at WRR control strategy in the reservoir of homogeneous, sealing.Early stage WRR target, at most about 2 years will be WRR=0.95.After 2 years, this target can rise to WRR=0.98.

Embodiment 2

The SAGD well of the simulation-a large amount of WLZ and vicinity that have also carried out SAGD technique in impaired bitumen reservoir is to being connected.The model hypothesis used is following:

(1) EXOTHERM ^tMsAGD mathematical model

(2) 30 meters of clean oil-producing areas; Dual well is to (Figure 12);

(3) WLZ damage is limited poor district, is connected, as shown in figure 12 with two SAGD well patterns;

(4) reservoir is homogeneous in other respects, K _h=5D; K _v=2.5D; S in Main Reservoirs ₀=80%; S in poor district ₀=15%;

(5) S in WLZ _w=85%;

(6) S in Main Reservoirs _w=20%; 15% can not restore, and 5% is variable;

(7) long=800 meters of well; Well interval=5 meter; Well pattern span=100 meter;

(8) for two wells pair, target SAGD pressure=2000kPa;

(9) for all case studies, excessively cold target constant (10 DEG C);

Run 5 cases (table 1), be summarized as follows:

The pressure of a case 1-base case=two well centering is identical (6 meters of thick WLZ, WLZ with shale lid are 10% of oil-producing area volume);

Case 2-allow well between the Δ Ρ of 300kPa;

The expection of case 2 (a)-output extends to 3 years+;

Case 3-is identical with case 2, but 1 year stops SAGD Stress control afterwards and changes constant fixing fabric structure (steam injection is constant) into;

Case 4-is identical with case 2, but WLZ is 3 meters thick (WLZ is 5% of oil-producing area volume);

Case 5-is identical with case 3, but WLZ be 3 meters thick;

Figure 13,14,15,16,17 and 18 show respectively for case 1,2,2 (a), 3, the right estimated performance of each well of 4 and 5.Figure 19 and 20 shows the right accumulation performance of two wells of case above.The accumulation asphalt production rate of Figure 21 and 22 display case 1 (base case) and case 2.Figure 23 shows the right WRR performance of each well of case 3.Figure 24 shows the accumulation WRR performance that case 1 contrasts case 3.Figure 25 shows the single well of case 3 to asphalt performance.

Based on Figure 13-25, should be noted that commentary below:

(1) in theory, Stress control is enough to SAGD.But being in fact difficult to pressure measxurement is the larger accuracy of about ± 200kPa (or about 10%).The hydrostatic head of 30 meters of reservoirs is about 335kPa.Natural side direction pressure drop in recovery well is maximum more than 50kPa.

(2) if there is active pool, then little pressure reduction can produce large difference.The pressure reduction of 300kPa is enough to overflow after about 1 year and at well to quenching SAGD in (Figure 14).

(3) Figure 15 shows the well of quenching to recovering afterwards for a long time.But steam injection stops (well is to 1) and steam flows through WLZ from well to 2.In fact, well is to the 1 experience steam overflow when about 540 days (1.5 years).

(4) impact of thickness on performance of WLZ is little.If compare Figure 14 and 17 and Figure 16 and 18, then for each well pair, performance factor is approximately identical.WLZ thickness is not sensible factor.

(5) if well is to behind 1 water blockoff, then steam is injected each well pair with fixed rate, some performance may be recovered (Figure 16).The method is converted to fixing fabric structure from Stress control.The replacement method realizing same effect is converted to WRR to control.

(6) if focus on accumulation performance (two well to together), then Figure 19 and 20 display equilibrium output case 1 is preferred route.Uneven output (between well Δ Ρ=300kPa) causes only about half of productivity ratio (Figure 26).Productivity ratio controls (case 3 and 5) by volume or WRR and can partly recover.WLZ thickness (case 2 is case 4 relatively) is not important variable.

(7) how Figure 23 affects WRR significantly if showing fixing fabric structure.Or its display WRR controls the fixing fabric structure how causing short-term.

(8) Figure 24 display is for accumulation well to (well to 1+ well to 2), and WRR feature is similar.

(9) how Figure 27 display improves the efficiency (as measured by SOR) of balancing run.

For purposes of the present invention, " seepage " SAGD well pattern is the well pattern of the water producing abnormal amount." seepage " SAGD well pattern can have the other parts of seepage entry/exit well pattern volume to reservoir; It can have seepage to/from contiguous reservoir SAGD well pattern; Or it can produce the water of the abnormal amount from WLZ in reservoir.In order to define " seepage " further, WRR will be used as indicator (water and the volume ratio injecting steam of generation, wherein steam use water-volume is measured).

As discussed above, for not having the homogeneous reservoir not having WLZ in fluid leaks and oil-producing area, Figure 10 shows expection WRR behavior.In early days the SAGD stage (100-300 days), WRR is between 0.90-0.95.During this period, GD vaporium is in formation, and GD district is in heating.The stock of aqueous water is created in reservoir.Along with the carrying out of SAGD method, WRR is increased to 0.99 gradually from about 0.96.If pitch space is only occupied by steam, then expection WRR is greater than 0.99 (Fig. 1).For SAGD later stage, bituminous production (and void content) is little, and WRR is close to the value (Figure 10) of 0.99.Between the SAGD peak period (500-1500 days), for the reasonable target of WRR-be about 0.97 of the SAGD GD room ideally included and homogeneous reservoir.

Figure 23 shows WRR in seepage reservoir and how seepage reservoir defines.If after the continuous SAGD that the use normal pressure in 200 or more skies controls, WRR depart from from 1.0 exceed ± 0.10, then reservoir is considered to " seepage ".Use this definition, in Figure 23, the simulation WRR performance of case 3 will cause thinking that two wells are " seepages " to well pattern.Well has higher WRR to 1, and well has the WRR lower than contrast 1.0 to 2.

Or if WLZ, top layer water or bottom water are placed in SAGD well pattern volume or neighbouring (Fig. 1) by existing geological knowledge, then SAGD well pattern can be regarded as " seepage " or potential " seepage ".

Another kind method is the connectivity (Aherne (2006)) using the test of cold water injectability to quantize SAGD well and WLZ, top layer water or bottom pool.This also may be used for assert that SAGD well pattern is " seepage " or potential " seepage ".

In seepage reservoir, Stress control SAGD (injecting vapour volume to obtain/to keep goal pressure) is disadvantageous.Can what there is in Figure 14 and 25 display seepage reservoir.Well to 1 (low pressure well pattern) by 1) from the water and 2 of WLZ) freely inject the water of contiguous well to the steam-condensation in 2 and overflow.After about 1 year, bituminous production is very little, and SOR is very high.After about 450 days, SAGD Stress control to stop steam injection to well in 1.Well produces pitch to 2 (vicinity, high pressure well patterns), but SOR is high.Finally, come artesian well to 2 steam penetrate into well to 1 (Figure 15), well restarts as pseudo-steam overflow the output of 1.

If compare two wells to the accumulation performance of (Figure 19, case 2 or case 4, Figure 20) and base case (case 1), then the SAGD Stress control observed in the seepage reservoir with WLZ cross-flow has caused lower column defects:

(1) the accumulation asphalt production rate reduced

(2) the accumulation pitch recovery ratio reduced

(3) SOR (efficiency of reduction) increased

(4) the aquatic products amount (water from WLZ) increased

On the other hand, if the pressure controlling each well centering makes to exist seldom or do not have cross-flow, then will improve and performance that each well of preferred optimization is right and the right accumulation performance (case 1) of two wells.But in fact, use SAGD Stress control to cause difficulty.The inflow/outflow of water can be there is under little barometric gradient, and be difficult to setting and gaging pressure target.There are 3 problems-1 in pressure) where gaging pressure; 2) tonometric accuracy; With 3) select correct pressure target.Even if for homogeneous reservoir, can expect vertically and side direction pressure reduction up to 300kPa (pressure reduction to simulation case Research Hypothesis).For active water invasion, Stress control can completely lose.Steam injection speed is constant can significantly affect well pattern pressure.

Another kind of control mechanism controls steam injection speed, do not depend on reservoir pressure.

Steam injection rate setting is fixed volume by Figure 16 and 18 display, even if at Stress control after 1 year, still can recover asphalt production rate and improve other performance factor.But, can partly play a role to some random and equal setting of volumetric rate target because two wells to well pattern be homogeneous with identical, except the WLZ be connected with the well pattern of institute research case.

Illustrate that the more rigorous method of some well pattern difference and mode use WRR to measure mode as setting target and the SAGD controlled in seepage reservoir to each well pattern, as follows:

(1) WRR of monitoring well pattern is continued, preferably weekly.

(2) after the continued operation more than 200 days, WRR is used to characterize well pattern reservoir (seepage or non-seepage).

(3) set target WRR (for the GD room included close to homogeneous, target WRR<1.0; For seepage well pattern, target WRR>1.0, to illustrate the output of the water from WLZ, top layer water or bottom water).

(4) if the WRR of actual well pattern is less than described target, then steam injection speed is reduced until reach described target.

(5) if the WRR of actual well pattern is greater than described target, then steam injection speed is increased until reach described target.

(6) most important consideration is certain mark that the pressure measured should not exceed reservoir separating pressure (be fracture pressure for cementing reservoir).Mark 0.8 is good safety margin.

Preferred embodiments more of the present invention also comprise

(1) early stage identification seepage reservoir (geology or water filling test)

(2) bitumen reservoir (<10API, >100,000cp)

(3) seepage reservoir is determined in time according to WRR performance

(4) carry out fixing fabric structure to steam injection, preferred WRR controls

(5) conventional SAGD method

(6) Athabasca pitch

Other embodiment of the present invention will be apparent for the person of ordinary skill of the art, and can be used by those skilled in the art and not deviate from spirit of the present invention.

form

Table 1:

WLZ simulation model case

Case 1 (base case)

-there is the thick poor district of water of 6 meters of 2 meters of shale lids

-SAGD crosses cold output and controls

-injection well pressure controls (2000kPa)

-two wells pair under 2000kPa

-except shale or WLZ the identical reservoir of all homogeneous

Case 2-(identical with case 1, except)

-well is 2200kPa (high pressure) to the pressure of 2

-well is 1900kPa (low pressure) to the pressure of 1

Case 2 (a)-(identical with case 2, except)

-extend running length to 3 year

Case 3-(identical with case 2, except)

Stress control is removed after-1 year, and to each well to injecting fixing and equal vapour volume case 4-(identical with case 2, except)

Thick 3 meters of-poor district

Case 5-(identical with case 3, except)

Thick 3 meters of-poor district

Table 2:

Poor district thermal conductivity

	[W/m℃]
		Poor district	2.88
Oil-producing area	1.09

Wherein

1. the water saturation of poor district=80%; The oil saturation of oil-producing area=80%

2.φ＝0.35

3. pair sandstone (quartz) reservoir, according to Butler (1991) algorithm.

Table 3:

Poor district thermal capacitance

Thermal capacitance	Oil-producing area	Poor district	% increases
				(kJ/kg)	1.004	1.254	24.9
(kJ/m 3)	2071.7	2584.7	24.8

Wherein:

1. use Butler algorithm (pressure (Butler, 1991) for pitch, water, sandstone).

2. suppose API=8.0, S.G.=1.0143

3. suppose T=25 DEG C

4. oil-producing area=35% porosity and 80% pitch saturation ratio

5. the porosity of poor district=35% and the water saturation of 80%

Claims (20)

1. water circulation is than the purposes for controlling at least one SAGD parameter in seepage bitumen reservoir.

2. control the method for the steam injection speed that single SAGD (SAGD) well is right in seepage bitumen reservoir, wherein said method comprises the Stress control of SAGD steam injection speed is replaced with the fixing fabric structure determined by water circulation ratio (WRR).

3. purposes according to claim 1, at least one parameter wherein said is selected from volumetric rate, pressure, temperature and its combination.

4. method according to claim 2, wherein said seepage bitumen reservoir is defined as seepage by least one of the geological knowledge of the poor district of water (WLZ) that scatters, top layer water or bottom water.

5. method according to claim 2, wherein said seepage bitumen reservoir injects test by the cold water before starting at SAGD and is defined as seepage.

6. method according to claim 2, wherein said seepage bitumen reservoir when through 200 days or more of a specified duration utilize the SAGD of Stress control steam injection to operate after, the change of WRR from 1.0 of SAGD be greater than 10% time, be considered to seepage.

7. method according to claim 2, wherein maintained cold control to liquid extraction.

8. method according to claim 2, wherein volumetric rate controls to realize by being injected into well by the steam injection SAGD of default target volume speed.

9., for controlling the method for the steam injection volumetric rate in SAGD (SAGD) technique in impaired reservoir, wherein said steam injection volumetric rate is by following control:

I. the water circulation ratio (WRR) that continuous measurement SAGD well is right;

Ii. the target of WRR is established; With

If iii. actual WRR is less than target WRR, then reduce steam injection speed until reach described target;

If iv. actual WRR is greater than target WRR, then increase steam injection speed until reach described target.

10. method according to claim 9, wherein said target WRR is between 0.9 and 1.0.

11. methods according to claim 9, wherein said target WRR is between 1.0 and 1.5.

12. methods according to claim 2, the seepage of wherein said seepage bitumen reservoir is the poor district of water (WLZ) owing to scattering in oil-producing area clean in described reservoir.

13. methods according to claim 2, the seepage of wherein said seepage bitumen reservoir is due to top layer pool.

14. methods according to claim 2, the seepage of wherein said seepage bitumen reservoir is due to bottom pool.

15. methods according to claim 2, the seepage of wherein said seepage bitumen reservoir is the many factors owing to comprising WLZ, top layer water and bottom water.

16. methods according to claim 2, wherein said pitch is API density <10 and the hydrocarbon of viscosity >100,000cp under natural reservoirs condition.

17. methods according to claim 8, SAGD pressure measured in wherein said reservoir is no more than:

I) for loose reservoir, reservoir separating pressure;

Ii) for cementing reservoir, reservoir fracture pressure.

18. methods according to claim 17, wherein measured SAGD pressure is no more than about 80% of described separating pressure or described fracture pressure.

19. methods according to claim 16, wherein said bitumen reservoir is positioned at the Athabasca area that Transport Model for Alberta is economized.

20. methods according to claim 2, wherein minimum operational pressure equals natural reservoir pressure.