CN109973059B - Rapid analysis method for gas injection mechanism of fracture-cavity oil reservoir - Google Patents

Rapid analysis method for gas injection mechanism of fracture-cavity oil reservoir Download PDF

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CN109973059B
CN109973059B CN201910249399.XA CN201910249399A CN109973059B CN 109973059 B CN109973059 B CN 109973059B CN 201910249399 A CN201910249399 A CN 201910249399A CN 109973059 B CN109973059 B CN 109973059B
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CN109973059A (en
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刘中云
王世洁
丁保东
赵海洋
刘宝增
冯一波
任波
王建海
何龙
焦保雷
秦飞
杨利萍
魏芳
马清杰
曾文广
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    • EFIXED CONSTRUCTIONS
    • E21EARTH OR ROCK DRILLING; MINING
    • E21BEARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
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    • E21B43/166Injecting a gaseous medium; Injecting a gaseous medium and a liquid medium
    • EFIXED CONSTRUCTIONS
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    • E21BEARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
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    • E21EARTH OR ROCK DRILLING; MINING
    • E21BEARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B47/00Survey of boreholes or wells
    • E21B47/12Means for transmitting measuring-signals or control signals from the well to the surface, or from the surface to the well, e.g. for logging while drilling
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Abstract

The invention particularly relates to a rapid analysis method for a gas injection mechanism of a fracture-cavity oil reservoir, which comprises the following steps: (1) acquiring single well drilling completion indexes, well logging indexes, exploitation indexes and/or water injection indexes of an oil well to be detected, and comprehensively judging possible reservoir types of the oil well to be detected according to 4 indexes, wherein the reservoir types comprise 3 types: karst cave, wide fracture and microfracture reservoirs; (2) testing the gas solubility and the miscible degree of single-well crude oil configured stratum live oil under the stratum condition; (3) and analyzing to obtain a gas injection mechanism according to the type of the reservoir body, the gas solubility and the miscible degree. The method can simply and accurately judge the type of the residual oil reservoir body and give out the mechanism of gas injection for crude oil exploitation, and has important guiding significance for deepening gas injection mechanism understanding and improving the effect of gas injection in the later period.

Description

Rapid analysis method for gas injection mechanism of fracture-cavity oil reservoir
Technical Field
The invention relates to the field of development of carbonate fracture-cavity oil reservoir nitrogen injection, in particular to a rapid analysis method of a fracture-cavity oil reservoir gas injection mechanism.
Background
The reservoir heterogeneity of the Tarim basin fracture-cavity carbonate rock reservoir is extremely strong, and the reservoir spaces are various, wherein a large-scale cave is the most main reservoir space, and cracks are main communicating channels; meanwhile, the oil-water relationship and the fluid flow characteristics of the oil reservoir are complex, so that the yield is greatly reduced, the primary recovery rate is low, and the implementation difficulty and the cost of other processes are high due to the 'two-over-three-high' characteristic of the oil reservoir. Therefore, nitrogen injection technology is implemented in 2012, and is now a replacing technology after water injection of the oil field of the Tahe river in the Tarim basin. Therefore, the method has important significance for deeply researching the nitrogen injection mechanism of the fracture-cavity oil reservoir and improving the understanding and the improving effect of the nitrogen injection of the fracture-cavity oil reservoir.
The existing research mainly comprises:
the fracture-cavity type oil reservoir residual oil reservoir body types are divided into loft oil, residual oil in a closed cavity, flow around oil, an oil film and residual oil at a filling position, a two-dimensional visual physical model and a three-dimensional visual physical model which are designed and manufactured are adopted, and the clear mechanism is formation energy supplement, gravity differentiation and replacement. (model Denyu, 2016, doctor's paper, research on fracture-cavity carbonate reservoir gas injection enhanced yield recovery technology and related mechanism)
A visual karst cave model of the fracture-cavity oil reservoir is adopted to simulate nitrogen foam flooding, and the main mechanism is gravity differentiation and reduction of interfacial tension. (Quming et al, report of Petroleum science 2018, vol.3, No. 1, research on parameters and mechanism of injection of Nitrogen foam into karst cave reservoirs of fracture-cave type reservoirs)
Aiming at the residual oil of attic oil, a numerical simulation method is adopted, and the main effects of the gas injection mechanism are mainly gravity differential displacement and energy supplement and phase mixing are defined as secondary effects. (Sunbo, 2014, Master thesis, gas injection and oil replacement mechanism and optimization research of fracture-cave type reservoir.)
The early gas injection mechanism analysis concentrates on the mechanism analysis of injecting nitrogen into karst cave type attic oil, and has the following problems: firstly, the type of the residual oil is separated from the actual type of the oil reservoir in a classification way, and actually, the type of the residual oil has an interwell crack type besides the attic oil; secondly, the physical simulation method is high in cost, and a high-temperature high-pressure device or a visualization device is generally required to be manufactured; thirdly, a numerical simulation method is adopted, a permeability equivalent method is generally adopted, a large number of parameters need to be adjusted, the labor and the labor are wasted, and the actual situation on site is separated; thirdly, in the practical application process, not only nitrogen gas is injected, but also other gases are injected to displace the crude oil.
Disclosure of Invention
In order to solve the problems, the invention provides a rapid analysis method for the gas injection mechanism of the fracture-cavity oil reservoir, which can simply and accurately judge the type of a residual oil reservoir body and give out the mechanism of gas injection for crude oil exploitation.
The invention adopts the following technical scheme:
a rapid analysis method for a gas injection mechanism of a fracture-cavity oil reservoir is characterized by comprising the following steps:
(1) acquiring single well drilling completion indexes, well logging indexes, exploitation indexes and/or water injection indexes of an oil well to be detected, and comprehensively judging possible reservoir types of the oil well to be detected according to 4 indexes, wherein the reservoir types comprise 3 types: karst cave, wide fracture and microfracture reservoirs;
(2) testing the gas solubility and the miscible degree of single-well crude oil configured stratum live oil under the stratum condition;
(3) analyzing to obtain a gas injection mechanism according to the type of the reservoir body, the gas solubility and the miscible degree;
the single well drilling and completion index refers to the drilling emptying or slurry loss speed in the drilling process;
the logging indexes refer to a natural gamma logging curve, a caliper logging curve, a resistivity logging curve, a sound wave logging curve, a neutron logging curve and a density logging curve of an oil well to be measured;
the mining index refers to the daily liquid yield and the accumulated liquid yield of the oil well to be detected;
the water injection index refers to daily water injection capacity and water injection pressure value of the oil well to be measured.
In the step (1), acquiring single well drilling completion indexes, well logging indexes, exploitation indexes and water injection indexes of an oil well to be detected, judging that the oil well to be detected accords with one of 3 reservoir types according to each 1 index of the oil well to be detected, and after 4 index judgment is completed, determining that the reservoir type result with the largest occurrence frequency is the possible reservoir type of the oil well to be detected.
In the step (1), the type of the possible reservoir body is judged according to the single well drilling and completion index, namely the drilling emptying or mud loss speed of the oil well to be detected in the drilling process,
when greater than 45m3When the oil well to be detected is a karst cave type reservoir body;
when the thickness is 25 to 45m3In the interval of/h, the oil well to be detected is a wide-crack type reservoir body;
when is greater than 5m3H is less than or equal to 25m3And h, the oil well to be detected is a micro-crack type reservoir body.
In the step (1), judging the types of the possible reservoirs according to the logging indexes, wherein the logging indexes comprise a natural gamma logging curve, a caliper logging curve, a resistivity logging curve, a sound wave logging curve, a neutron logging curve and a density logging curve, the judgment result of each curve shows that the oil well to be detected belongs to one of 3 reservoirs, and the results of the types of the possible reservoirs are determined by the types of the majority of reservoirs according to the conditions shown in the following table;
GR and KTH of a natural gamma logging curve of the oil well to be detected are 5-15API, U is larger than 15API, and the variation amplitude of each curve except GR is larger than 50%, so that the curve is a micro-crack type reservoir body; GR and KTH are 5-15API, and radioactive uranium content is 10-15AP, and the wide crack type reservoir body is formed; GR and KTH are 30-135API, jagged or peak-like and large wavy changes, and the energy spectrum index shows that radioactive uranium elements are more than 15API, and the radioactive uranium elements are karst cave type reservoirs;
the logging curve of the borehole diameter of the oil well to be measured shows that the borehole diameter is expanded by less than 5 percent or is slightly jagged, and the oil well is a micro-crack type reservoir body; the diameter of the well is expanded by less than 10 percent or is slightly jagged, and the well is a wide fracture type reservoir body; the diameter of the well is expanded by more than 20 percent or abnormally increased, and the well is a karst cave type reservoir body;
the resistivity logging curve of the oil well to be detected shows that the resistivity is 500-800 omega m, the curve change is severe, and if the curve changes in a positive way, the curve is a micro-crack type reservoir body; the resistivity is 500-800 omega m, the curve change is severe, and if the curve changes in a positive way, the curve is a wide fracture type reservoir body; the resistivity is less than 200 omega m, and the solution cavity type reservoir bodies are formed if the resistivity is obviously positive;
displaying the acoustic logging curve of the oil well to be tested, wherein the acoustic wave is smaller than 50us/ft, and the micro-crack type reservoir body is obtained; the sound wave is a wide fracture type reservoir body at 50-65 us/ft; when the sound wave is more than 50us/ft, the karst cave type reservoir body is formed;
displaying a neutron logging curve of the oil well to be detected, wherein a microcrack reservoir is formed when the neutron is less than 2%; 2% -6% of neutrons are wide fracture type reservoirs; if the neutron is more than 6%, the solution cavity type reservoir body is formed; the density of the oil well to be measured is shown by a logging curve, and the density is more than 2.69g/cm3A microfracture-type reservoir; the density is 2.55-2.69g/cm3Then a wide fracture type reservoir; the curve is in a negative peak shape and is less than 2.55g/cm3Then is a karst cave type reservoir body;
in the step (1), judging the mining indexes according to the mining indexesPossible reservoir type, liquid production capacity of greater than 45m on the day3Judging the fluid to be a karst cave type reservoir body when the fluid is more than 2 ten thousand tons; the liquid production capacity of the day is 25-45 m3Judging the fluid to be a wide-crack type reservoir body when the fluid is produced in a per hour and the accumulated production fluid is 1-2 ten thousand tons; the liquid production capacity of the day is less than 25m3And judging the micro-fracture type reservoir body when the accumulated production liquid is less than 1 ten thousand tons at the time of/h.
In the step (1), the possible reservoir body type is judged according to the water injection index, and the water injection capacity in the same day is more than 45m3Judging the karst cave type reservoir body when the pressure of water injection is less than 1 MPa; the water injection capacity in the same day is 25-45 m3Judging the wide fracture type reservoir body when the pressure of water injection is 1-10 MPa; the water injection capacity in the same day is less than 25m3And when the pressure is more than 10MPa, judging the micro-fracture reservoir body.
In the step (2), single-well crude oil is selected to prepare stratum live oil, a high-temperature high-pressure thin tube displacement experiment is adopted under stratum conditions, the miscible degree is judged, the miscible displacement is judged if the recovery ratio is larger than or equal to 90%, and the immiscible displacement is judged if the recovery ratio is smaller than 90%.
In the step (3), if it is judged as a karst cave type reservoir, the gas solubility is 80m3/m3The following is a gravity differentiation mechanism and is non-miscible displacement; if the reservoir is judged to be a wide fracture type reservoir, the gas solubility is 80m3/m3The following mechanism of non-miscible displacement is to inhibit water coning and change the mechanism of an oil reservoir flow field;
if judged as a microcracked reservoir, the gas solubility is 80m3The following non-miscible displacement is realized by utilizing the penetration and expansion energizing mechanism of gas; if the reservoir is judged to be micro-fractured, the gas solubility is more than 80m3And the miscible displacement is the dissolution and expansion mechanism of gas and crude oil.
The gas solubility and the miscible degree are obtained by a gas-crude oil phase state experiment and a thin tube displacement experiment.
The invention discloses a method for quickly analyzing a gas injection mechanism of a fracture-cavity oil reservoir. The method comprises the steps of judging the type of a reservoir body according to single-well drilling and completion indexes, well logging indexes, exploitation indexes and water injection indexes, further judging the type of single-well residual oil, selecting single-well crude oil to configure formation live oil, carrying out a gas-crude oil phase experiment and a thin tube displacement experiment, judging the gas solubility and the miscible degree, and finally giving a nitrogen injection mechanism based on technical analysis according to the single-well residual oil type, the phase experiment and the thin tube experiment scheme. The method has important guiding significance for deepening the understanding of the mechanism of gas injection body displacement crude oil and improving the later nitrogen injection effect.
Drawings
FIG. 1a schematic representation of a nitrogen injection mechanistic process for cavernous reservoir types;
FIG. 1 a: before nitrogen injection; FIG. 1 b: injecting nitrogen;
FIG. 2 is a graphical illustration of a nitrogen injection mechanism for wide fracture type reservoir types;
FIG. 2 a: before nitrogen injection; FIG. 2 b: injecting nitrogen;
FIG. 3 is a graphical representation of a nitrogen injection mechanistic process for a micro-fractured reservoir type;
FIG. 3 a: before nitrogen injection; FIG. 3 b: injecting nitrogen;
FIG. 4a graphical representation of the micro-fractured reservoir type CO2 injection mechanization process;
FIG. 4 a: before CO2 injection; FIG. 4 b: after CO2 is injected;
1-gas, 2-water, 3-crude oil, 4-oil-CO2And (3) mixing.
Detailed Description
For a more clear understanding of the present invention, specific embodiments thereof are now described in detail, without limiting the scope of the invention thereto.
Example 1: rapid analysis method for gas injection mechanism of fracture-cavity oil reservoir 1
(1) Comprehensively judging the type of the reservoir according to the well completion index, the logging index, the exploitation index and the water injection index of the single well;
1) single well drilling and completion indicator
The 1# oil well is positioned at the north edge of a Tarim basin, the drilling is finished in 5-17 th month in 1999, the drilling completion well depth is 5612.7m, and the drilling completion layer is an Ordovician lower system; in the drilling process, 5410-5420m is emptied and malignant loss occurs (the mud loss speed is higher than that of the mud45m3And/h), the type of the reservoir is judged to be a karst cave type according to the single well drilling and completion index, and the possible type of the reservoir is judged to be a karst cave type according to the single well drilling and completion index.
2) Logging index
TABLE 1 determination of logging indicators
Figure BDA0002011967600000051
Logging indicators show 5410-5420m, natural Gamma (GR) logging, high value response (30-135API), jagged or spiky and large waviness; the energy spectrum index shows that the content of partial radioactive uranium element (U) is high (more than 15API) (soluble cavity type); the hole diameter is measured, the hole expansion is obvious (more than 20%) (cave-dissolving type); the resistivity value is lower and is 50 omega m, the abnormal reduction is realized, and the 'positive difference' (cave-dissolving type) is obvious; sonic, higher response characteristics, 120us/ft (cave-in); neutrons present high-value response characteristics, greater than 3% (tunnel type); density logging, low value response characteristic, negative spike shape, numerical value of 2.3g/cm3(cavern type), therefore, the possible reservoir type is judged to be cavern type according to the logging index.
3) Index of exploitation
Oil is produced in a combined manner after well completion, and the daily production of crude oil in the initial stage is 62m3Then pumping production until 2 months (2012), 44.61 × 104t, cumulative oil yield 17.65X 104 tTherefore, the possible reservoir type is judged to be the karst cave type according to the mining index.
4) Index of water injection
The oil is replaced by water injection from 9/12 2006, at present, 7 times of oil replacement is performed, the water injection pressure is 0, even the oil is sucked reversely, and therefore the possible reservoir body type is judged to be the karst cave type according to the water injection index.
And judging through drilling and completion indexes, logging indexes, production indexes and water injection indexes, wherein possible types of the reservoirs are all karst cave types, and further judging that the type of the well reservoir is the karst cave type.
(2) Testing the gas solubility and the miscible degree of the single-well crude oil configured formation live oil under the formation condition;
1) experiment for measuring crude oil phase state of nitrogen-1 # oil well by adopting high-temperature high-pressure PVT (pressure-volume-velocity-flow)
High temperature high pressure PVT apparatus: the visual window of the PVT test unit is made of high-pressure quartz glass, the maximum volume is 300mL, the window volume of the PVT test unit is 90mL, and the dead volume of the PVT test unit is less than 10 mL. The upper limit of the working pressure is 70MPa, and the upper limit of the temperature measurement is 200 ℃. The piston which can move up and down is arranged in the testing unit, and the pressure in the visual testing unit and the volume of the PVT testing unit can be adjusted by adjusting the position of the piston. A thermocouple is arranged in the testing device and is used for detecting the temperature of a system in the visual PVT testing unit, and the measuring precision is +/-0.3 ℃. The system pressure is measured by a precision pressure sensor, and the system pressure precision is +/-0.01 MPa. The volume of the oil phase in equilibrium is read by a CCD camera system with a volume accuracy of + -0.001 mL.
And (3) testing conditions are as follows: 120 ℃ and 60 MPa;
and (3) measuring results: the solubility of nitrogen in crude oil of 1# oil well under formation conditions is 42m3/m3
2) Adopts high-temperature high-pressure tubule experiment to judge the miscible phase degree
High temperature high pressure tubule displacement experimental apparatus: an injection pump system: the Ruska full-automatic pump has the working pressure of 0-70.00 MPa, the working temperature of room temperature and the speed precision of 0.001 mL; a back pressure regulator: the working pressure is 0-70.00 MPa, and the working temperature is room temperature-200.0 ℃; a pressure difference meter: the maximum working pressure difference is 34.00MPa, and the working temperature is room temperature; a temperature control system: the working temperature is between room temperature and 200.0 ℃, and the temperature control precision is 0.1 ℃;
and (3) testing conditions are as follows: 120 ℃ and 60 MPa;
and (3) measuring results: the displacement effect of nitrogen on the crude oil No. 1 is that the recovery ratio is 62 percent, and the product is immiscible.
(3) The well residual oil type is karst cave type residual oil, the nitrogen solubility is low, and nitrogen injection is unmixed phase displacement.
Further analysis shows that the density of nitrogen under the oil reservoir condition of the well at 120 ℃ and 60MPa is 0.35g/cm2The karst cave type residual oil is mainly concentrated at the high part of the karst cave, after nitrogen is injected, the solubility of the nitrogen in the crude oil is low, the nitrogen replaces the head space, the crude oil descends,and (3) recovering the production of the oil well, wherein the nitrogen injection mechanism of the well is unmiscible gravity differentiation, and the specific implementation process is shown in figure 1.
In FIG. 1, FIG. 1a is a schematic diagram of a karst cave type residual oil, the oil-water interface is raised above the overflow point of an oil production well, and the residual oil at the high part cannot be used; FIG. 1b shows that after nitrogen injection, the oil-water interface is lowered by the gravity separation mechanism, and crude oil is produced.
Example 2: rapid analysis method for gas injection mechanism of fracture-cavity oil reservoir 2
(1) Comprehensively judging the type of the reservoir according to the well completion index, the logging index, the exploitation index and the water injection index of the single well;
1) single well drilling and completion indicator
The No. 2 oil well is positioned at the north edge of the Tarim basin and belongs to the same oil reservoir as the No. 1 oil well. Completing drilling at 11/27 th of 2005, wherein the drilling depth is 5915m, and the drilling layer is the Ordovician lower system. During the drilling process, when the drilling reaches 5878m, the loss occurs, and the loss speed is 32.5m3After strong drilling to 5915.0m, leakage to 437.8m3Mud, no blow-down, so the likely reservoir type is judged to be wide fracture type according to single well drilling and completion indicators.
2) Logging index
The judgment indexes are as shown in Table 1.
Logging indexes show that 5878-5915m, gamma logging, GR (natural gamma) and KTH (no uranium gamma) values are low (5-15API), and radioactive uranium content (10-15API) is certain (wide crack type); the well diameter is expanded or slightly jagged (the expanded diameter is less than 10 percent) (wide crack type); the resistivity is low-the median fluctuates by 500-800 omega m, the curve changes more violently, changes by more than 50%, and presents positive difference (wide crack type or micro crack type); the sound wave value is increased and fluctuates between 50 and 65us/ft (wide crack type or solution type); neutron logging, with increased or slightly increased values (between 2% and 6%) (wide fracture type); density logging, between 2.55 and 2.69g/cm3(wide fracture type), the wide fracture type is most when the type of the reservoir is judged according to the logging index, so the logging index judges that the possible type of the reservoir is the wide fracture type.
3) Index of exploitation
After completion, the self-injection production is carried out, the conventional well completion is carried out, 35 t/day of daily production fluid at the initial stage, 27-day in 2006 stops injection and rotary pumping (CYB-56/38TH multiplied by 2300m), and the production fluid 19347t, the oil 10441t and the water 8906t are accumulated until the nitrogen is injected. The likely reservoir type is therefore judged to be a wide fracture type based on production criteria.
4) Index of water injection
The water injection pressure cone is carried out in 11 months in 2008, water injection is stopped because the adjacent TK643 well quickly rises due to water containing, and 969m of accumulated water injection is carried out3And the average water injection pressure is 5MPa, so that the possible reservoir type is judged to be a wide fracture type according to the water injection index.
The well is judged by drilling and completion indexes, logging indexes, exploitation indexes and water injection indexes, and is all in a wide fracture type, and the type of the well reservoir body is further judged to be in the wide fracture type.
(2) Testing the gas solubility and the miscible degree of the single-well crude oil configured formation live oil under the formation condition;
the phase state experiment of the crude oil of the nitrogen-1 # oil well is measured by adopting high-temperature and high-pressure PVT, and the measurement result shows that the solubility of the nitrogen in the crude oil of the 1# oil well under the stratum condition is 45m3(ii) a The displacement effect of nitrogen on the No. 1 crude oil is measured by adopting a high-temperature high-pressure tubule experiment, the recovery ratio is 67 percent, and the nitrogen is in a non-miscible phase.
(3) The well residual oil type is wide crack type residual oil, the nitrogen solubility is low, and nitrogen injection is non-miscible displacement.
Further analysis shows that the density of nitrogen under the oil reservoir condition of the well at 120 ℃ and 65MPa is 0.36g/cm2The wide crack type residual oil is mainly concentrated at a local high part, and in the early production process, because the water contained in the oil well is steeply flooded or quickly rises when the production pressure difference is overlarge, a water cone is formed, so that a large amount of residual oil on the two sides of the water cone cannot be extracted; in the process of nitrogen injection and oil extraction, the water cone is inhibited by nitrogen, the mechanism of an oil reservoir flow field is changed, the form of the bottom water cone is changed, the pressure field around the well is promoted to be redistributed, the height of the water cone is reduced, and therefore the extraction of the residual oil on two sides of the water cone around the well is realized, and the specific implementation process is shown in fig. 2.
In FIG. 2, FIG. 2a is a schematic diagram of a wide crack type residual oil, the bottom water energy is strong, the water content rises rapidly due to an excessive production pressure difference, a water cone is formed, and the residual oil on two sides of the water cone cannot be extracted; and FIG. 2b shows that after nitrogen is injected, the water cone shape of bottom water is changed by utilizing the water cone inhibition of nitrogen and the oil reservoir flow field mechanism, the water cone height is reduced, and crude oil is produced.
Example 3 Rapid analysis method of gas injection mechanism of fracture-cavity reservoir 3
(1) Comprehensively judging the type of the reservoir according to the well completion index, the logging index, the exploitation index and the water injection index of the single well;
1) single well drilling and completion indicator
The 3# well oil well is positioned at the north edge of the Tarim basin and belongs to the same oil reservoir as the 1# and 2# oil wells. Finishing drilling in 9 and 30 days in 2008, finishing drilling the well depth of 6011m, and finishing drilling the layer of the Ordovician lower system. During drilling, when the drilling depth reaches 5956m, the loss of mud is 15.75m3Leakage occurs when drilling to 6002m, leakage section: 6002-6011m, cumulative lost circulation slurry 86.25m3The mud loss speed in the drilling process is between 5 and 25m3And/h, therefore, the possible reservoir type is judged to be micro-fractured according to the single well completion index.
2) Logging index
The judgment indexes are as shown in Table 1.
The logging indexes are 5945.0-6011.0m, gamma logging is performed, GR and KTH values are 5-15API, U is larger than 15API, and curves except GR are large in change (micro-crack type); the diameter expansion is less than 5 percent (wide crack type and micro crack type); the resistivity is low-to-medium (550-800 ohm m), the curve changes more violently, and the curve is in positive difference (wide crack type and micro crack type); the sound wave value fluctuates from 10 to 25us/ft (microcrack type); neutron logging, with values less than 0.05% (microcrack type); density log with value greater than 2.69g/cm3(microcrack type). Therefore, the microcrack type is the majority, and the possible reservoir type is judged to be the microcrack type according to the logging index.
3) Index of exploitation
After completion, the self-injection production is carried out, the conventional completion is carried out, 15 t/day of the initial daily liquid production is carried out, the pumping is carried out in a modifying and transferring way (CYB-56/38TH multiplied by 2300m) on 11-7 days in 2008, and before nitrogen injection, 3781t of the cumulative liquid production and 1757t of the produced oil are carried out. Therefore, the type of the reservoir body is judged to be a cavern type according to the mining index, and the type of the possible reservoir body is judged to be a micro-crack type according to the mining index.
4) Index of water injection
The water injection pressure cone is injected in 12 months in 2008, water is injected for 6 times, and water is injected for 1172m in average period3And the average water injection pressure is 11MPa, so that the possible reservoir type is judged to be a micro-crack type according to the water injection index.
The method is characterized in that the well drilling and completion index, the well logging index, the exploitation index and the water injection index are judged, the micro-crack type possibly accounts for most of the reservoir types, and the type of the well reservoir is further judged to be the micro-crack type.
(2) Testing the gas solubility and the miscible degree of the single-well crude oil configured formation live oil under the formation condition;
the crude oil phase state experiment of the nitrogen-3 # oil well is measured by adopting high-temperature and high-pressure PVT, and the measurement result shows that the solubility of nitrogen in the crude oil of the 3# oil well under the stratum condition is 65m3/m3(ii) a The displacement effect of nitrogen on the 3# crude oil is measured by adopting a high-temperature high-pressure tubule experiment, the recovery ratio is 73 percent, and the nitrogen is in a non-miscible phase.
3) The well residual oil type is micro-crack type residual oil, the nitrogen solubility is low, and nitrogen injection is non-miscible displacement.
Further analysis shows that the density of nitrogen under the oil reservoir condition of the well at 120 ℃ and 65MPa is 0.36g/cm2The micro-fracture type residual oil is mainly concentrated at a local high part, in the early production process, because the pressure of a production formation is reduced, the fracture is closed or blocked, the continuity of liquid supply is poor, and the residual oil at the far end cannot be extracted, in the nitrogen gas injection oil extraction process, the water drive wave and the crude oil in the fracture hole which cannot be extracted are excited by using the penetration and expansion energizing mechanism of nitrogen gas, so that the extraction of the residual oil at the far end around the well is realized, and the specific mechanism process is shown in fig. 3.
In fig. 3, fig. 3a is a schematic diagram of residual oil in micro-fracture type, the fracture is closed or blocked due to the formation pressure drop, and the residual oil at the far end cannot be extracted; and fig. 3b shows that after nitrogen is injected, the nitrogen penetration and expansion energizing mechanism of nitrogen is utilized to activate the crude oil in the fracture cavity which cannot be reached by water flooding so as to realize the extraction of the residual oil at the far end of the well periphery.
Example 4 fast analysis method of gas injection mechanism of fracture-cavity reservoir 4
(1) Comprehensively judging the type of the reservoir according to the well completion index, the logging index, the exploitation index and the water injection index of the single well;
1) single well drilling and completion indicator
The 1# oil well is positioned at the north edge of a Tarim basin, the drilling is finished in 5-17 th month in 1999, the drilling completion well depth is 5612.7m, and the drilling completion layer is an Ordovician lower system; in the drilling process, 5410-5420m is emptied and malignant loss occurs (the mud loss speed is more than 45 m)3H), the possible reservoir type is judged to be karst cave type according to the single well drilling and completion index.
2) Logging index
The judgment indexes are as shown in Table 1.
Logging indicators show 5410-5420m, natural Gamma (GR) logging, high value response (30-135API), jagged or spiky and large waviness; the energy spectrum index shows that part of radioactive uranium element is high in content (more than 15API) (soluble cavity type); the hole diameter is measured, the hole expansion is obvious or abnormally increased (more than 20%) (cave-in type); the resistivity value is lower and is 50 omega m, the abnormal reduction is realized, and the 'positive difference' (cave-dissolving type) is obvious; sonic, higher response characteristics, 120us/ft (cave-in); neutrons present high-value response characteristics, greater than 3% (tunnel type); density logging, low value response characteristic, negative spike shape, numerical value of 2.3g/cm3(cavern type), and therefore the possible reservoir type is judged to be cavern type according to the logging index.
3) Index of exploitation
Oil is produced in a combined manner after well completion, and the daily production of crude oil in the initial stage is 62m3Then pumping production until 2 months (2012), 44.61 × 104t, cumulative oil yield 17.65X 104And t, judging the type of the reservoir body to be a karst cave type according to the mining index, and judging the possible type of the reservoir body to be the karst cave type according to the mining index.
4) Index of water injection
The oil is replaced by water injection from 9/12 in 2006, and at present, the oil is replaced by water injection for 7 times, the water injection pressure is 0, even the oil is sucked backwards, so that the possible reservoir body type is judged to be the karst cave type according to the water injection index, and the possible reservoir body type is judged to be the karst cave type according to the water injection index.
And judging the well reservoir type to be a karst cave type through the drilling and completion index, the logging index, the exploitation index and the water injection index, wherein the karst cave type possibly accounts for most of the reservoir types.
(2) Testing the gas solubility and the miscible degree of the single-well crude oil configured formation live oil under the formation condition;
CO determination using high temperature high pressure PVT2Crude oil phase experiment of No. 1 oil well, the measurement result shows that the solubility of nitrogen in the crude oil of No. 1 oil well under the formation condition is 150m3(ii) a CO determination by high-temperature high-pressure tubule experiment2The recovery ratio of the displacement effect on the No. 1 crude oil is 92 percent, and the oil is a mixed phase.
(3) The residual oil type of the well is karst cave type residual oil and CO2High solubility, CO injection2Is miscible displacement.
For further analysis, CO2The density of the oil deposit under the well oil deposit condition is 0.81g/cm at 120 ℃ and 60MPa2The residual oil in karst cave is mainly concentrated at the high part of the karst cave, and the density of the residual oil in karst cave is 0.79g/cm2Injection of CO2After then, CO2High solubility in crude oil and CO2Density similar to that of crude oil, CO2Fully dissolving and mixing with crude oil, mixing phase to form a phase state, dissolving and expanding, recovering production of oil well after well opening, and recovering CO2CO produced simultaneously with crude oil, pressure reduction, dissolved CO2The specific implementation process of expansion precipitation is shown in FIG. 4.
In FIG. 4, FIG. 4a is a schematic diagram of a karst cave type residual oil, the oil-water interface is raised above the overflow point of the oil production well, and the residual oil at the high position cannot be used; FIG. 4b is CO injection2After then, CO2Dissolving and expanding with crude oil, and extracting crude oil.

Claims (6)

1. A rapid analysis method for a gas injection mechanism of a fracture-cavity oil reservoir is characterized by comprising the following steps:
(1) acquiring single well drilling completion indexes, well logging indexes, exploitation indexes and water injection indexes of an oil well to be detected, and comprehensively judging possible reservoir types of the oil well to be detected according to 4 indexes, wherein the reservoir types comprise 3 types: karst cave, wide fracture and microfracture reservoirs;
(2) testing the gas solubility and the miscible degree of single-well crude oil configured with formation live oil under the formation condition;
(3) analyzing to obtain a gas injection mechanism according to the type of the reservoir body, the gas solubility and the miscible degree;
in the step (1), acquiring single well drilling completion indexes, well logging indexes, exploitation indexes and water injection indexes of an oil well to be detected, judging that the oil well to be detected accords with one of 3 reservoir types according to each 1 index of the oil well to be detected, and after 4 index judgment is completed, determining that the reservoir type result with the largest occurrence frequency is the possible reservoir type of the oil well to be detected;
in the step (3), if it is judged as a karst cave type reservoir, the gas solubility is 80m3/m3The following is a gravity differentiation mechanism and is non-miscible displacement; if the reservoir is judged to be a wide fracture type reservoir, the gas solubility is 80m3/m3The following mechanism of non-miscible displacement is to inhibit water coning and change the mechanism of an oil reservoir flow field; if judged as a microcracked reservoir, the gas solubility is 80m3The following non-miscible displacement is realized by utilizing the penetration and expansion energizing mechanism of gas; if the reservoir is judged to be micro-fractured, the gas solubility is more than 80m3And is miscible displacement, namely a gas and crude oil dissolution expansion mechanism;
the single well drilling and completion index refers to the drilling emptying or slurry loss speed in the drilling process;
the logging indexes refer to a natural gamma logging curve, a caliper logging curve, a resistivity logging curve, a sound wave logging curve, a neutron logging curve and a density logging curve of an oil well to be measured;
the mining index refers to the daily liquid yield and the accumulated liquid yield of the oil well to be detected;
the water injection index refers to daily water injection capacity and water injection pressure value of the oil well to be measured.
2. The method for rapidly analyzing the gas injection mechanism of the fractured-vuggy reservoir according to claim 1, wherein in the step (1), the possible reservoir type is judged according to the single well drilling and completion index, namely the drilling emptying or mud loss speed of the oil well to be tested in the drilling process,
when the drilling is empty or the mud loss speed is more than 45m3When the oil well to be detected is a karst cave type reservoir body;
when the drilling emptying or slurry loss speed is 25-45 m3In the interval of/h, the oil well to be detected is a wide-crack type reservoir body;
when the drilling is empty or the mud loss speed is more than 5m3H is less than or equal to 25m3And h, the oil well to be detected is a micro-crack type reservoir body.
3. The method for rapidly analyzing the gas injection mechanism of the fractured-vuggy reservoir according to claim 1, wherein in the step (1), the possible reservoir type is judged according to the exploitation index, and the daily liquid production capacity is more than 45m3Judging the fluid to be a karst cave type reservoir body when the fluid is more than 2 ten thousand tons; the liquid production capacity of the day is 25-45 m3Judging the fluid to be a wide-crack type reservoir body when the fluid is produced in a per hour and the accumulated production fluid is 1-2 ten thousand tons; the liquid production capacity of the day is less than 25m3And judging the micro-fracture type reservoir body when the accumulated production liquid is less than 1 ten thousand tons at the time of/h.
4. The method for rapidly analyzing the gas injection mechanism of the fractured-vuggy reservoir according to claim 1, wherein in the step (1), the possible reservoir types are judged according to the water injection indexes, and the daily water injection capacity is more than 45m3Judging the karst cave type reservoir body when the pressure of water injection is less than 1 MPa; the water injection capacity in the same day is 25-45 m3Judging the wide fracture type reservoir body when the pressure of water injection is 1-10 MPa; the water injection capacity in the same day is less than 25m3And when the pressure is more than 10MPa, judging the micro-fracture reservoir body.
5. The method for rapidly analyzing the gas injection mechanism of the fracture-cavity oil reservoir according to claim 1, wherein in the step (2), single-well crude oil is selected to prepare formation live oil, a high-temperature high-pressure tubule displacement experiment is adopted under formation conditions, the miscible degree is judged, the mixed-phase displacement is judged when the recovery ratio is larger than or equal to 90%, and the non-mixed-phase displacement is judged when the recovery ratio is smaller than 90%.
6. The method for rapidly analyzing the gas injection mechanism of the fracture-cavity oil reservoir according to any one of claims 1 to 5, wherein the gas solubility and the miscible degree are respectively obtained by a gas-crude oil phase experiment and a thin tube displacement experiment.
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