A kind of critical water injection pressure calculation method of oil-gas anticlinal deposits crack elimination
Technical field
The present invention relates to a kind of oil-gas field development field, specifically a kind of critical water filling pressure of oil-gas anticlinal deposits crack elimination
Power calculation method.
Background technique
During oil extraction in oil field, by disposing between water injection well and producing well according to certain rule, stratum can be kept
The recovery ratio in oil field is improved while pressure, biggish water injection pressure can improve the efficiency of oil recovery in a short time.However, part oil
Slit band is extremely developed in the reservoir of field, and after water injection pressure reach a certain height, crack may as the natural plane of weakness of rock
It opens, causes injection water along slit band quickly through reducing sweep efficiency, cause producing well High water cut in a short time.Therefore,
It determines reasonable water injection pressure, recovery ratio can be improved to greatest extent.The present invention proposes a kind of oil-gas anticlinal deposits crack elimination
Critical water injection pressure calculation method.
Summary of the invention
The purpose of the present invention is to provide a kind of critical water injection pressure calculation methods of oil-gas anticlinal deposits crack elimination, with solution
Certainly the problems mentioned above in the background art.
To achieve the above object, the invention provides the following technical scheme:
A kind of critical water injection pressure calculation method of oil-gas anticlinal deposits crack elimination comprising the steps of:
A, it on the basis of considering well point fracture strike, filling operation statistics, establishes crack and ruptures again and water injection pressure
Model;
B, by dividing tectonic position to count well point crustal stress, it is determined that fill the water pressure between anticlinal high and both wings oils water boundary
The range of power;
C, for local cracks with respect to dense region, comparison pressure break well point minimum burst pressure and the critical water filling of anticlinal high
The relationship of pressure;
D, the method for proposing to calculate dense band critical water injection pressure in crack under different condition;
E, for anticline, locally more phase tectonic stresses are superimposed, and fracture strike is regional in a jumble, propose to determine crack endpoint stress
Deviation approach and any method for moving towards crack breakthrough pressure of calculating, and determine the critical water injection pressures in these areas.
As further technical solution of the present invention: the step B is specifically: divide tectonic position statistics well point now most
Minor principal stress, maximum principal stress, and the critical water injection pressure near anticlinal high and alar part oils water boundary is calculated, determine anticlinal belt
The distribution of critical water injection pressure.
As further technical solution of the present invention: in the step C: the critical water injection pressure of comparison anticlinal high and well point
Pressure minimum burst pressure relationship, the method for determining the critical water injection pressure in crack compact district under different condition, and safe guarantor is set
Protect threshold value.
As further technical solution of the present invention: the safeguard protection threshold value is 5MPa.
As further technical solution of the present invention: the step D is specifically: the crustal stress for calculating crack compact district is inclined
Difference determines the calculation method of the mixed and disorderly critical water injection pressure in area of more phase Stress superpositions, fracture strike.
As further technical solution of the present invention: the model in step A includes: crack elimination water filling critical pressure meter
It is infused when calculation, anticlinal oil pool fracture reservoir water injection pressure calculate, dense band critical water injection pressure in crack calculates and fracture strike is mixed and disorderly
Water pressure calculation.
As further technical solution of the present invention: the critical condition of gash fracture are as follows: Δ Ρ=σf, σfIt is broken for slit band
Resistance to spalling, it is related with the Filling Characteristics in crack;Δ Ρ is that fracture surface eliminates the tensile residual stresses after skeleton pressure.
Compared with prior art, the beneficial effects of the present invention are: the present invention is considering well point fracture strike, filling operation system
On the basis of meter, establishes crack and rupture again and the model of water injection pressure;By dividing tectonic position to count well point crustal stress, really
The range of water injection pressure between anticlinal high and both wings oils water boundary is determined;For local cracks with respect to dense region, compare pressure
The relationship of well point minimum burst pressure Yu the critical water injection pressure of anticlinal high is split, proposes that calculating crack dense band under different condition faces
The method of boundary's water injection pressure;For arch structure part, the mixed and disorderly area of more phase tectonic stress superpositions, fracture strike is proposed true
Determine crack endpoint stress-deviation method, calculates any determining critical water injection pressure in this area on the basis of moving towards crack breakthrough pressure.
Specific embodiment
The technical scheme in the embodiments of the invention will be clearly and completely described below, it is clear that described implementation
Example is only a part of the embodiment of the present invention, instead of all the embodiments.Based on the embodiments of the present invention, this field is common
Technical staff's every other embodiment obtained without making creative work belongs to the model that the present invention protects
It encloses.
Embodiment 1: a kind of critical water injection pressure calculation method of oil-gas anticlinal deposits crack elimination, this method are considering well point
On the basis of fracture strike, filling operation statistics, establishes crack and rupture again and the model of water injection pressure;By dividing formations
Position statistics well point crustal stress, it is determined that the range of water injection pressure between anticlinal high and both wings oils water boundary;For local cracks
Opposite dense region, compares the relationship of pressure break well point minimum burst pressure and the critical water injection pressure of anticlinal high, proposes different items
The method of the critical water injection pressure of crack dense band is calculated under part;For anticline, locally more phase tectonic stress superpositions, fracture strike are miscellaneous
Disorderly area proposes to determine crack endpoint stress-deviation method and calculates any method for moving towards crack breakthrough pressure, and determined
The critical water injection pressure in these areas.
Specific as follows: 1. crack eliminations fill the water critical pressure computation model:
In the injecting process, because pressure is excessive, after balancing the frame stress in stratum, such as still above rupture strength, then may be used
Rupture can be generated, the tonguing of injection water body is caused.In the injecting process, shaft bottom is not much different along well ambient pressure, when crack is deposited
When, be the position that stratum is easiest to rupture, when pit shaft internal pressure power overcomes to fall perpendicular to fracture surface as the plane of weakness on stratum
After compression, slit band rupture strength is such as still greater than, crack further extends, and the critical condition of gash fracture is then are as follows:
Δ Ρ=σf (1)
In formula (1): σfIt is related with the Filling Characteristics in crack for slit band rupture strength;Δ Ρ is that fracture surface eliminates skeleton
Tensile residual stresses after pressure meet respectively:
σf=C* σT (2)
Δ Ρ=Ρ-Ρf (3)
In formula (2): σTFor the tensile strength of reservoir rock, can be obtained according to laboratory test results;C is frac-pack
Coefficient, less than 1, value is influenced the numerical value by the filling operation, charges type, filling method of slit band, when charges with enclose
Lithofacies like when, which is infinitely close to 1, the tensile strength of gash fracture intensity infinite approach reservoir rock, which can be with
Empirical value is provided after observing by rock core.
In formula (3): P bottom pressure;ΡfThe stress in vertical fracture face meets:
σ1: horizontal maximum principal stress;σ2: horizontal minimum principal stress;σ1、σ2It can test to obtain by well point, θ: crack normal
Transmeridional angle is deviated, can be calculated after well point counts fracture strike with formula (5):
(5)
Formula (1), (2), (4) are substituted into (3), shaft bottom critical pressure P should are as follows:
2. anticlinal oil pool fracture reservoir water injection pressure calculates:
The stress distribution now of oil-gas anticlinal deposits is uneven, shallower close to anticline axle portion buried depth, and close to both wings with depth
Degree increases, and corresponding triaxial stress increases in various degree.In the stress statistic processes of well point, it should tectonic position be divided to unite
Meter, nearby well point is one group to high point, seeks corresponding maximum and minimum principal stress, water filling critical pressure corresponds to formula (7), and carries on the back
Oblique both wings are another group close to oils water boundary position well point, read corresponding stress, and water filling critical pressure corresponds to formula (8).
It will be in formula (7), (8): PHigh point、σ1 high point、σ2 high pointsRespectively correspond the critical water injection pressure near anticlinal high, maximum is led
Stress, minimum principal stress;PIt is black、σ1 wing、σ2 wingsThen correspond to critical water injection pressure of the flank of anticline near oils water boundary, maximum main
Stress, minimum principal stress.Under normal conditions, high point nearby fills the water critical pressure and corresponds to minimum value Pmin, and it is right near oils water boundary
Answer Pmax。
By taking Ao Nan anticlinal oil pool as an example, fracture strike α assembly average in well point is NE65 °;Crack fills crack with half
Based on, volumetric efficiency C value is 0.5;Reservoir siltstone, laboratory test tensile strength σTFor 3.89MPa;Read anticlinal high
Principal stress greatest around is 30Mpa, minimum principal stress 18Mpa, and near alar part oils water boundary, corresponding maximum, most
Minor principal stress is respectively 37MPa, 23MPa.According to formula (5), (7), (8), critical note near the anticlinal high can be calculated
Water pressure is 22.06MPa, and the critical water injection pressure of alar part is 27.42Mpa, therefore the best water injection pressure of the oil reservoir should collect
In between 22.06~27.42MPa.
3. dense band critical water injection pressure in crack calculates:
The fracture development of reservoir is extremely uneven in oil-gas anticlinal deposits, the part region relatively intensive there may be crack,
In the injecting process crack dense band is likely to form stress concentration, so that many cracks be caused to be connected to, injection water is along newly penetrating through
Slit band quickly propels.In addition, oil field in seismic data interpretation, is influenced by seismic data resolution, it is difficult to identify that turn-off is small
In the tomography of 5m, therefore the safeguard protection section of 5MPa is set, the critical water injection pressure in crack compact district takes:
ΡIt is close=ΡHigh point-5 (9)
Reference should be made to pressure break situations while if wellblock there are pressure break data, considers tectonic position, when fracture pressure is small
When anticlinal high critical pressure, close quarters critical water injection pressure in crack is taken:
ΡIt is close=ΡIt is broken-5 (10)
In formula (10): ΡIt is brokenFor the well point fracture pressure minimum value read in pressing crack construction process.High point critical pressure and pressure
Caused by deviation when splitting between minimum burst pressure is crack or craven fault endpoint stress concentration.That is:
Ρf0=PHigh point-PIt is broken (11)
In formula (11): Ρf0Refer to pressure divergence caused by crack or craven fault both ends stress concentration.
By taking Ao Nan oil-gas anticlinal deposits as an example, critical water injection pressure is 22.06Mpa near the high point that is calculated, and well point
Pressure break data shows that fracture pressure is distributed between 19~43MPa, minimum burst pressure 19MPa, which is less than high point critical
Pressure, therefore determine that crack dense band water injection pressure nearby, the numerical value are 14MPa using formula (10), corresponding crack is concentrated
Stress-deviation Ρ caused by bandf0For 3.06Mpa.
Embodiment 2, on the basis of embodiment 1, since oil and gas reservoir experienced more phase tectonic movements after deposition,
The most area fracture strike of anticline has predominant direction, however very mixed and disorderly in fracture strike, needs to calculate any trend
The cracking pressure in crack.Water injection pressure calculates as follows when fracture strike is mixed and disorderly:
Any fracture strike α, normal direction θ is α+90, after considering slit band problem of stress concentration, corresponding critical pressure
Power ΡαMeet:
Still by taking Ao Nan oil-gas anticlinal deposits as an example, biggest principal stress direction is approximately EW, minimum principal stress now for this area
Direction is nearly north-south.Parameters in formula (11) it is known that any fracture strike critical pressure only with crack with answer now
Power angle is related.It can be calculated that the crack of south-north direction (α=0) is vertical with maximum principal stress, cracking pressure is up to
28.89MPa;East-west crack is parallel with maximum principal stress (α=90), has the smallest cracking pressure 16.89MPa.?
On the basis of this, according to formula (9) can calculate fracture strike it is mixed and disorderly when, corresponding water filling critical pressure be 11.89MPa.
It is obvious to a person skilled in the art that invention is not limited to the details of the above exemplary embodiments, Er Qie
In the case where without departing substantially from spirit or essential attributes of the invention, the present invention can be realized in other specific forms.Therefore, no matter
From the point of view of which point, the present embodiments are to be considered as illustrative and not restrictive, and the scope of the present invention is by appended power
Benefit requires rather than above description limits, it is intended that all by what is fallen within the meaning and scope of the equivalent elements of the claims
Variation is included within the present invention.
In addition, it should be understood that although this specification is described in terms of embodiments, but not each embodiment is only wrapped
Containing an independent technical solution, this description of the specification is merely for the sake of clarity, and those skilled in the art should
It considers the specification as a whole, the technical solutions in the various embodiments may also be suitably combined, forms those skilled in the art
The other embodiments being understood that.