CN109884109A - A kind of shale hole water adsorption amount, free amount and its evaluation method of distribution - Google Patents
A kind of shale hole water adsorption amount, free amount and its evaluation method of distribution Download PDFInfo
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Abstract
The present invention relates to shale pore water preservation and its quantitative assessment technical fields, disclose a kind of shale hole water adsorption amount, free amount and its evaluation method of distribution, it proposes and describes movable water with the mathematic(al) representation, ratio of adsorption equation and equation of state for liquids of centrifugal pressure difference, on this basis, simultaneous nuclear magnetic resonance spin spinrelaxation T2Expression formula is established based on nuclear magnetic resonance T2Liquid water adsorption amount, free amount and its evaluation method of distribution in the shale matrix pores of spectrum.Using nuclear magnetic resonance T2Detection shale absorption water and free water content and its distribution that can be quick, lossless is composed, easy to operation, accuracy is high, and operability, practicability are stronger, promotes and applies convenient for geology.
Description
Technical field
The present invention relates to shale pore water preservation and its quantitative assessment technical fields, and in particular to a kind of shale pore water suction
Attached amount, free amount and its evaluation method of distribution.
Background technique
Shale gas mainly the free gas with preservation in intrinsic fracture and matrix hole-crack and is adsorbed in organic matter/clay
Based on the adsorbed gas of particle surface, wherein adsorbed gas can account for 30-60%；Containing a small amount of solution gas, can be ignored.Adsorbed gas and free gas
As the material base of shale gas exploitation, their content in situ and its migration (flowing) process is by the shale reservoir property of water-bearing
Significantly affect, and then affect shale gas yield, constrain the high-efficiency mining of shale gas.Production practices also show initial aqueous
Saturate shale air content is low, well yield is low (such as China Zhaotong block)；The low shale gassiness of initial water saturation
Amount is high, there are obvious superpressure, well yield height (such as China Changning-Weiyuan, rich and smooth-Yongchuan block).Therefore, the aqueous situation of shale
It is a key factor for influencing shale gas high-efficiency mining.
Before shale gas exploitation, need to be transformed reservoir the exploitation for being just able to achieve and having an economic benefit.North America at present
The remodeling method generally used with the country is horizontal well drilling completion combination large hydraulic fracturing.It is domestic generally to use oil base drilling well
Liquid, but aqueous fracturing fluid is used in fracturing reform, the scale of " thousand side's sand of all places water " is needed during entire reservoir reconstruction, and
The row of returning leads very low.A large amount of fracturing fluid (water content > 90%) is stranded in stratum.Due to the characteristic of shale Abnormal low water saturation
Shale hole capillary imbibition power is considerably increased, after fracturing fluid touches rock surface, the water self-priming under capillary force immediately
Into shale matrix, leads to water saturation increase in shale near nearly well band or fracture surface, forms water phase blocking in duct,
It is serious to reduce gas phase permeability.Therefore, in addition to the influence of shale reservoir connate water, the injection of outside fluid exacerbates shale reservoir
Aqueous complexity and its influence degree to shale gas exploitation.
Although hydraulic fracturing transformation significantly extends, linked up shale reservoir Fracture System, matrix pores are involved journey
Degree is still very limited, and therefore, can a large amount of residual gas effectively be employed in shale matrix pores, will greatly be controlled by matrix
The regularity of distribution of water in hole.But it is current mainly to pass through initial water saturation, irreducible water saturation, movable water saturation both at home and abroad
The macroparameters such as degree evaluate the shale property of water-bearing.In view of the complexity, multiple dimensioned property and strong heterogeneity of shale microstructure,
Matrix pores water adsorption amount, free amount and its micro Distribution are evaluated, realistic meaning is had more for shale gas high-efficiency mining.It is domestic
Outer scholar has carried out many pilot studies for the adsorption/desorption that steam condition (relative pressure) is lauched, and then evaluates water and exist
The intrapore regularity of distribution of shale/mineral；And for the regularity of distribution of the liquid water in hole in shale formation, due to lacking reason
By evaluation model, corresponding experimental study is also very deficient.
Shale pore water, which can be divided into, adsorbs water and free water, and hardly flowable on absorption water theory, free water is theoretically
It is flowable.But free water is influenced by shale pore throat microstructure, in external condition (such as centrifugal force, displacement pressure, rock matrix
Stress) under flowable part be moveable water；Not flowable part is hollow billet irreducible water.Hollow billet irreducible water is with external condition
Change, moveable water can be converted into.Therefore the movable water of theoretical maximum is equal to free water content.The present invention considers shale matrix pores
The occurrence status of interior liquid water and the flowability of different conditions pore water are based on nuclear magnetic resonance T2Spectrum, proposes a kind of shale
Liquid water adsorption amount, free amount and its evaluation method of distribution in matrix pores.
Summary of the invention
Based on problem above, the present invention provides a kind of shale hole water adsorption amount, free amount and its evaluation method of distribution,
It establishes based on nuclear magnetic resonance T2Liquid water adsorption amount, free amount and its evaluation method of distribution in the shale matrix pores of spectrum,
Easy to operation, accuracy is high, and operability, practicability are stronger, promotes and applies convenient for geology.
In order to solve the above technical problems, the present invention provides a kind of shale hole water adsorption amount, free amount and its distributions
Evaluation method includes the following steps:
Step 1: shale column rock core is dried, measurement shale core quality in the dry state and page
The NMR signal of rock rock core；
Step 2: under the conditions of certain temperature, by the shale core saturated water under drying regime, shale core saturation is tested
Water QtWith the NMR signal of shale core under saturated-water phase；
Step 3: watery according to being saturated in the NMR signal of shale core under drying regime in step 1 and step 2
The NMR signal of shale core under state, by going substrate inverting to obtain the nuclear magnetic resonance T of shale core pore water2Spectrum；Page
Nuclear magnetic resonance spin spinrelaxation T in rock rock core hole2Calculation formula are as follows:
Wherein, T2For spin spinrelaxation, ms；ρ is surface relaxivity, nm/ms；SwFor the specific surface area containing water voids, Vw
For the volume containing water voids；
Step 4: test is centrifuged in the shale core of saturated water in step 2, it is poor to obtain different centrifugal pressures
Movable water content Q under △ P-conditionm, establish the functional relation between movable water and centrifugal pressure difference:
Wherein, QmFor movable water, mg/g；QfFor water of dissociating, i.e., maximum movable water, mg/g；△ P is centrifugal pressure
Difference, MPa；△PLCorresponding centrifugal pressure is poor when reaching the half of maximum movable water for movable water, MPa；
The data that centrifuge test obtains are substituted into functional relation and the progress between movable water and centrifugal pressure difference
Fitting, obtains free water content Qf；According to absorption water content, free water content, the ratio of adsorption r of centrifuge test is calculateda:
Wherein, water content Q is adsorbedaThen pass through formula Qa=Qt-QfIt calculates；
Step 5: using the specific surface area S containing water voids of low temperature nitrogen adsorption/desorption method test shale corew, use
The volume V containing water voids of weight in wet base method and low temperature nitrogen adsorption/desorption method integration test shale corew；For the page of saturated water
Rock rock core, in absorption water account for the mass ratio of total Water and may be expressed as:
Wherein, H is average adsorption thickness, nm；ρ1And ρ2It is absorption water and free water averag density, g/cm respectively3；
Simultaneous formula (3) and (4) can must describe the equation of state for liquids of liquid occurrence status:
Wherein, τ is correction coefficient, for parallel planar hole, value 1, Vw/SwWith Qf/QaBetween it is in a linear relationship when, τ
Close to 1；
Step 6: it is based on nuclear magnetic resonance T2Spectrum, simultaneous equation of state for liquids calculate each T2Corresponding absorption water contains when value
Amount and free water content, and absorption water saturation, free water saturation are respectively with T2The distribution of value；Calculation process are as follows:
Simultaneous formula (1) and (4) can obtain:
Based on nuclear magnetic resonance T2Spectrum, in conjunction with formula (6), can calculate nuclear magnetic resonance T2Each T in spectrum2It is worth corresponding absorption
Ratio indicates are as follows:
Wherein, T2iFor nuclear magnetic resonance T2Compose upper i-th of T2Value；raiFor T2iIt is worth corresponding ratio of adsorption, score；0<rai≤
1, as calculated value raiWhen > 1, r is takenai=1；
Nuclear magnetic resonance T2Each T in spectrum2It is worth corresponding absorption water signal amplitude (Mai) are as follows:
Mai=Mirai (8)
Wherein, MiFor i-th of T2It is worth corresponding resultant signal amplitude (mass normalisation, similarly hereinafter)；MaiFor i-th of T2Value corresponds to
Absorption water signal amplitude (mass normalisation, similarly hereinafter)；
Based on formula (8), the absorption water that can calculate shale core accounts for the mass ratio of total Water:
Wherein, ra(T2) it is based on nuclear magnetic resonance T2The mass ratio that absorption water in the shale core calculated accounts for total Water is composed, point
Number；MtiFor nuclear magnetic resonance T2Compose upper i-th of T2It is worth corresponding absorption water signal amplitude；N is nuclear magnetic resonance T2Compose inverting points；
Determine best surface relaxation rate, constraint equation are as follows:
δ=| ra(T2)-ra| (10)
δ value when different surfaces Relaxivity values is analyzed, when the suction of the nuclear magnetic resonance ratio of adsorption calculated and centrifugal process test
When the absolute value δ of attached proportional difference is equal to 0 or infinitely approaches 0, best surface Relaxivity values can be obtained.
Best Relaxivity values are substituted into formula (8), each T can be obtained2It is worth corresponding absorption water signal amplitude (Mai).Meanwhile
Free water signal amplitude (M can be obtainedfi), are as follows:
Mfi=Mti-Mai (11)
Wherein, MfiFor i-th of T2It is worth corresponding absorption water signal amplitude；
According to the linear relationship between signal amplitude and water content, each T can be calculated2When value corresponding absorption water content and
Free water content, and with T2The distribution of value.Relationship between signal amplitude and water content may be expressed as:
Y=kx (12)
Wherein, y represents the water content of unit mass shale core, mg/g；X represents the signal width of unit mass shale core
Degree；K is fitting coefficient；
Then adsorb water content and distribution calculation formula are as follows:
Qai=kMai (13)
Wherein, QaiFor i-th of T2It is worth corresponding absorption water content, mg/g；
Free water content and distribution calculation formula are as follows:
Qfi=kMfi (14)
Wherein, QfiFor i-th of T2It is worth corresponding free water content, mg/g；
Water saturation is adsorbed with T2The distribution calculation formula of value are as follows:
Wherein, φaiFor i-th of T2It is worth corresponding absorption water saturation, %；
Water saturation of dissociating is with T2The distribution calculation formula of value are as follows:
φfi=1- φai (16)
Wherein, φfiFor i-th of T2It is worth corresponding absorption water saturation, %.
Further, shale core is saturated 24~48h of distilled water at 20 °C in step 1.
Further, shale core drying condition is dried for 24 hours under the conditions of being 110 DEG C in step 1.
Compared with prior art, the beneficial effects of the present invention are: based on shale core pore water occurrence status and flowable
Property feature, in conjunction with nuclear magnetic resonance T2Spectral structure, establish shale matrix pores water adsorption amount under laboratory condition, free amount and
Its evaluation method being distributed, easy to operation, accuracy is high, and operability, practicability are stronger, promotes and applies convenient for geology.
Detailed description of the invention
Fig. 1 is the relational graph of movable water and centrifugal pressure difference in embodiment 2；
Fig. 2 is V in embodiment 2w/SwWith Qf/QaBetween relational graph；
Fig. 3 be embodiment 2 in nuclear magnetic resonance calculate with centrifuge test obtain ratio of adsorption difference absolute value δ with
The variation diagram of Surface Relaxation rate；
Fig. 4 be embodiment 2 in rock core S1 absorption water and free water content with T2The distribution map of value；
Fig. 5 be embodiment 2 in rock core S2 absorption water and free water content with T2The distribution map of value；
Fig. 6 be embodiment 2 in rock core S3 absorption water and free water content with T2The distribution map of value；
Fig. 7 be embodiment 2 in rock core S4 absorption water and free water content with T2The distribution map of value；
Fig. 8 be embodiment 2 in rock core S5 absorption water and free water content with T2The distribution map of value；
Fig. 9 be embodiment 2 in rock core S6 absorption water and free water content with T2The distribution map of value；
Figure 10 is shale water content and signal amplitude relational graph in embodiment 2；
Figure 11 is the absorption water of rock core S1 in embodiment 2 and free water saturation with T2The distribution map of value；
Figure 12 is the absorption water of rock core S2 in embodiment 2 and free water saturation with T2The distribution map of value；
Figure 13 is the absorption water of rock core S3 in embodiment 2 and free water saturation with T2The distribution map of value；
Figure 14 is the absorption water of rock core S4 in embodiment 2 and free water saturation with T2The distribution map of value；
Figure 15 is the absorption water of rock core S5 in embodiment 2 and free water saturation with T2The distribution map of value；
Figure 16 is the absorption water of rock core S6 in embodiment 2 and free water saturation with T2The distribution map of value.
Specific embodiment
To make the objectives, technical solutions, and advantages of the present invention clearer, below with reference to embodiment and attached drawing, to this
Invention is described in further detail, and exemplary embodiment of the invention and its explanation for explaining only the invention, are not made
For limitation of the invention.
Embodiment 1:
A kind of shale hole water adsorption amount, free amount and its evaluation method of distribution, include the following steps:
Step 1: shale column rock core is dried, measurement shale core quality in the dry state and page
The NMR signal of rock rock core；
Step 2: under the conditions of certain temperature, by the shale core saturated water under drying regime, shale core saturation is tested
Water QtWith the NMR signal of shale core under saturated-water phase；
Step 3: watery according to being saturated in the NMR signal of shale core under drying regime in step 1 and step 2
The NMR signal of shale core under state, by going substrate inverting to obtain the nuclear magnetic resonance T of shale core pore water2Spectrum；Page
Nuclear magnetic resonance spin spinrelaxation T in rock rock core hole2Calculation formula are as follows:
Wherein, T2For spin spinrelaxation, ms；ρ is surface relaxivity, nm/ms；SwFor the specific surface area containing water voids, Vw
For the volume containing water voids；
Step 4: test is centrifuged in the shale core of saturated water in step 2, it is poor to obtain different centrifugal pressures
Movable water content Q under △ P-conditionm, establish the functional relation between movable water and centrifugal pressure difference:
Wherein, QmFor movable water, mg/g；QfFor water of dissociating, i.e., maximum movable water, mg/g；△ P is centrifugal pressure
Difference, MPa；△PLCorresponding centrifugal pressure is poor when reaching the half of maximum movable water for movable water, MPa；
The data that centrifuge test obtains are substituted into functional relation and the progress between movable water and centrifugal pressure difference
Fitting, obtains free water content Qf；According to absorption water content, free water content, the ratio of adsorption r of centrifuge test is calculateda:
Wherein, water content Q is adsorbedaThen pass through formula Qa=Qt-QfIt calculates；
Step 5: using the specific surface area S containing water voids of low temperature nitrogen adsorption/desorption method test shale corew, use
The volume V containing water voids of weight in wet base method and low temperature nitrogen adsorption/desorption method integration test shale corew；For the page of saturated water
Rock rock core, in absorption water account for the mass ratio of total Water and may be expressed as:
Wherein, H is average adsorption thickness, nm；ρ1And ρ2It is absorption water and free water averag density, g/cm respectively3；
Simultaneous formula (3) and (4) can must describe the equation of state for liquids of liquid occurrence status:
Wherein, τ is correction coefficient, for parallel planar hole, value 1, Vw/SwWith Qf/QaBetween it is in a linear relationship when, τ
Close to 1；
Step 6: it is based on nuclear magnetic resonance T2Spectrum, simultaneous equation of state for liquids calculate each T2Corresponding absorption water contains when value
Amount and free water content, and absorption water saturation, free water saturation are respectively with T2The distribution of value；Calculation process are as follows:
Simultaneous formula (1) and (4) can obtain:
Based on nuclear magnetic resonance T2Spectrum, in conjunction with formula (6), can calculate nuclear magnetic resonance T2Each T in spectrum2It is worth corresponding absorption
Ratio indicates are as follows:
Wherein, T2iFor nuclear magnetic resonance T2Compose upper i-th of T2Value；raiFor T2iIt is worth corresponding ratio of adsorption, score；0<rai≤
1, as calculated value raiWhen > 1, r is takenai=1；
Nuclear magnetic resonance T2Each T in spectrum2It is worth corresponding absorption water signal amplitude (Mai) are as follows:
Mai=Mirai (8)
Wherein, MiFor i-th of T2It is worth corresponding resultant signal amplitude (mass normalisation, similarly hereinafter)；MaiFor i-th of T2Value corresponds to
Absorption water signal amplitude (mass normalisation, similarly hereinafter)；
Based on formula (8), the absorption water that can calculate shale core accounts for the mass ratio of total Water:
Wherein, ra(T2) it is based on nuclear magnetic resonance T2The mass ratio that absorption water in the shale core calculated accounts for total Water is composed, point
Number；MtiFor nuclear magnetic resonance T2Compose upper i-th of T2It is worth corresponding absorption water signal amplitude；N is nuclear magnetic resonance T2Compose inverting points；
Determine best surface relaxation rate, constraint equation are as follows:
δ=| ra(T2)-ra| (10)
δ value when different surfaces Relaxivity values is analyzed, when the suction of the nuclear magnetic resonance ratio of adsorption calculated and centrifugal process test
When the absolute value δ of attached proportional difference is equal to 0 or infinitely approaches 0, best surface Relaxivity values can be obtained.
Best Relaxivity values are substituted into formula (8), each T can be obtained2It is worth corresponding absorption water signal amplitude (Mai).Meanwhile
Free water signal amplitude (M can be obtainedfi), are as follows:
Mfi=Mti-Mai (11)
Wherein, MfiFor i-th of T2It is worth corresponding absorption water signal amplitude；
According to the linear relationship between signal amplitude and water content, each T can be calculated2When value corresponding absorption water content and
Free water content, and with T2The distribution of value.Relationship between signal amplitude and water content may be expressed as:
Y=kx (12)
Wherein, y represents the water content of unit mass shale core, mg/g；X represents the signal width of unit mass shale core
Degree；K is fitting coefficient；
Then adsorb water content and distribution calculation formula are as follows:
Qai=kMai (13)
Wherein, QaiFor i-th of T2It is worth corresponding absorption water content, mg/g；
Free water content and distribution calculation formula are as follows:
Qfi=kMfi (14)
Wherein, QfiFor i-th of T2It is worth corresponding free water content, mg/g；
Water saturation is adsorbed with T2The distribution calculation formula of value are as follows:
Wherein, φaiFor i-th of T2It is worth corresponding absorption water saturation, %；
Water saturation of dissociating is with T2The distribution calculation formula of value are as follows:
φfi=1- φai (16)
Wherein, φfiFor i-th of T2It is worth corresponding absorption water saturation, %.
Embodiment 2:
On the basis of embodiment 1, by taking five peak group of south China marine facies-Longma small stream group, 6 shale column rock cores as an example:
Step 1: carrying out that shale core is dry for 24 hours under the conditions of 110 DEG C first, test dry shale core quality and
The NMR signal of shale core；
Step 2: being saturated distilled water for 24 hours at 20 °C, and the quality of test saturation shale core calculates saturated water amount
For Qt(being shown in Table 1)；Meanwhile testing the NMR signal of saturation shale core；
Step 3: watery according to being saturated in the NMR signal of shale core under drying regime in step 1 and step 2
The NMR signal of shale core under state, by going substrate inverting to obtain the nuclear magnetic resonance T of shale core pore water2Spectrum；
Step 4: being directed to 6 shale cores, carries out the centrifuge separation test under different centrifugal pressure differences respectively, uses
Formula (2) fitting centrifugation data are as shown in Figure 1, obtain free water content QfIt is shown in Table 1；According to formula Qa=Qt-QfCalculate absorption water
Content QaIt is shown in Table 1；
Step 5: low temperature nitrogen adsorption/desorption and weight in wet base method are used, the volume V containing water voids of shale core is testedwWith
Specific surface area S containing water voidsw；
Step 6: it is based on nuclear magnetic resonance T2Spectrum, simultaneous equation of state for liquids calculate each T2Corresponding absorption water contains when value
Amount and free water content, and absorption water saturation, free water saturation are respectively with T2The distribution of value, specific calculation process is such as
Under:
According to formula (5), V is establishedw/SwWith Qf/QaBetween linear functional relation as shown in Fig. 2, may be expressed as: y=
0.9972x+0.6475；
According to the V of acquisitionw/SwWith Qf/QaBetween linear functional relation, in conjunction with free water density p under the conditions of 20 DEG C2For
0.9982g/cm3, the equal density p of adsorption levels can be calculated1For 1.5402g/cm3, average adsorption thickness H is 0.6475nm；
In conjunction with nuclear magnetic resonance T2Spectrum substitutes into formula (7)~(9) using different Surface Relaxation rate values；When calculated result is full
It is best surface relaxation rate ρ (being shown in Table 1) when δ value in sufficient formula (10) is equal to 0.
1 shale core water content centrifuge test of table and nuclear magnetic resonance spectroscopy tables of data
The absolute value (i.e. δ value) for the ratio of adsorption difference that the ratio of adsorption and centrifuge test that nuclear magnetic resonance calculates obtain
Variation tendency with different surfaces relaxation rate is as shown in Figure 3；
Obtained best Relaxivity values are substituted into formula (7) and formula (11), absorption water signal amplitude can be calculated separately out, dissociated
Water signal amplitude and with T2The distribution of value is as shown in Fig. 4~9；
The relationship established between signal amplitude and water content is as shown in Figure 10, may be expressed as: y=0.0293x；
According to the relationship between signal amplitude and water content, using formula (13) and (14), calculate separately out absorption water and
Free water content and with T2The distribution of value is as shown in Fig. 4~9；
According to formula (15), absorption water saturation is calculated with T2Figure 11~16 are shown in the distribution of value；
According to formula (16), free water saturation is calculated with T2Figure 11~16 are shown in the distribution of value.
It as above is the embodiment of the present invention.Design parameter in above-described embodiment and embodiment is merely to understand table
Invention verification process is stated, the scope of patent protection being not intended to limit the invention, scope of patent protection of the invention is still with it
It is all to change with equivalent structure made by specification and accompanying drawing content of the invention subject to claims, it should all similarly wrap
Containing within the scope of the present invention.
Claims (3)
1. a kind of shale hole water adsorption amount, free amount and its evaluation method of distribution, which comprises the steps of:
Step 1: shale column rock core is dried, measurement shale core quality in the dry state and shale rock
The NMR signal of the heart；
Step 2: under the conditions of certain temperature, by the shale core saturated water under drying regime, shale core saturated water amount is tested
QtWith the NMR signal of shale core under saturated-water phase；
Step 3: according under saturated-water phase in the NMR signal of shale core under drying regime in step 1 and step 2
The NMR signal of shale core, by going substrate inverting to obtain the nuclear magnetic resonance T of shale core pore water2Spectrum；Shale rock
Nuclear magnetic resonance spin spinrelaxation T in heart hole2Calculation formula are as follows:
Wherein, T2For spin spinrelaxation, ms；ρ is surface relaxivity, nm/ms；SwFor the specific surface area containing water voids, VwFor containing
The volume of water voids；
Step 4: being centrifuged test for the shale core of saturated water in step 2, obtains different centrifugal pressure difference △ P items
Movable water content Q under partm, establish the functional relation between movable water and centrifugal pressure difference:
Wherein, QmFor movable water, mg/g；QfFor water of dissociating, i.e., maximum movable water, mg/g；△ P is that centrifugal pressure is poor,
MPa；△PLCorresponding centrifugal pressure is poor when reaching the half of maximum movable water for movable water, MPa；
By centrifuge test obtain data substitute into movable water and centrifugal pressure difference between functional relation and be fitted,
Obtain free water content Qf；According to absorption water content, free water content, the ratio of adsorption r of centrifuge test is calculateda:
Wherein, water content Q is adsorbedaThen pass through formula Qa=Qt-QfIt calculates；
Step 5: using the specific surface area S containing water voids of low temperature nitrogen adsorption/desorption method test shale corew, using weight in wet base
The volume V containing water voids of method and low temperature nitrogen adsorption/desorption method test shale corew；For the shale core of saturated water,
The mass ratio that interior absorption water accounts for total Water may be expressed as:
Wherein, H is average adsorption thickness, nm；ρ1And ρ2It is absorption water and free water averag density, g/cm respectively3；
Simultaneous formula (3) and (4) can must describe the equation of state for liquids of liquid occurrence status:
Wherein, τ is correction coefficient, for parallel planar hole, value 1, Vw/SwWith Qf/QaBetween it is in a linear relationship when, τ is close
In 1；
Step 6: it is based on nuclear magnetic resonance T2Spectrum, simultaneous equation of state for liquids calculate each T2When value corresponding absorption water content and
Free water content, and absorption water saturation, free water saturation are respectively with T2The distribution of value；Calculation process are as follows:
Simultaneous formula (1) and (4) can obtain:
Based on nuclear magnetic resonance T2Spectrum, in conjunction with formula (6), can calculate nuclear magnetic resonance T2Each T in spectrum2It is worth corresponding ratio of adsorption,
It indicates are as follows:
Wherein, T2iFor nuclear magnetic resonance T2Compose upper i-th of T2Value；raiFor T2iIt is worth corresponding ratio of adsorption, score；0<rai≤ 1, work as meter
Calculation value raiWhen > 1, r is takenai=1；
Nuclear magnetic resonance T2Each T in spectrum2It is worth corresponding absorption water signal amplitude (Mai) are as follows:
Mai=Mirai (8)
Wherein, MiFor i-th of T2It is worth corresponding resultant signal amplitude (mass normalisation, similarly hereinafter)；MaiFor i-th of T2It is worth corresponding suction
Attached water signal amplitude (mass normalisation, similarly hereinafter)；
Based on formula (8), the absorption water that can calculate shale core accounts for the mass ratio of total Water:
Wherein, ra(T2) it is based on nuclear magnetic resonance T2Compose the mass ratio that absorption water in the shale core calculated accounts for total Water, score；
MtiFor nuclear magnetic resonance T2Compose upper i-th of T2It is worth corresponding absorption water signal amplitude；N is nuclear magnetic resonance T2Compose inverting points；
Determine best surface relaxation rate, constraint equation are as follows:
δ=| ra(T2)-ra| (10)
δ value when different surfaces Relaxivity values is analyzed, when the absorption ratio of the nuclear magnetic resonance ratio of adsorption calculated and centrifugal process test
When the absolute value δ of example difference is equal to 0 or infinitely approaches 0, best surface Relaxivity values can be obtained.
Best Relaxivity values are substituted into formula (8), each T can be obtained2It is worth corresponding absorption water signal amplitude (Mai).Meanwhile it can obtain
Free water signal amplitude (Mfi), are as follows:
Mfi=Mti-Mai (11)
Wherein, MfiFor i-th of T2It is worth corresponding absorption water signal amplitude；
According to the linear relationship between signal amplitude and water content, each T can be calculated2Corresponding absorption water content and free when value
Water content, and with T2The distribution of value.Relationship between signal amplitude and water content may be expressed as:
Y=kx (12)
Wherein, y represents the water content of unit mass shale core, mg/g；X represents the signal amplitude of unit mass shale core；k
For fitting coefficient；
Then adsorb water content and distribution calculation formula are as follows:
Qai=kMai (13)
Wherein, QaiFor i-th of T2It is worth corresponding absorption water content, mg/g；
Free water content and distribution calculation formula are as follows:
Qfi=kMfi (14)
Wherein, QfiFor i-th of T2It is worth corresponding free water content, mg/g；
Water saturation is adsorbed with T2The distribution calculation formula of value are as follows:
Wherein, φaiFor i-th of T2It is worth corresponding absorption water saturation, %；
Water saturation of dissociating is with T2The distribution calculation formula of value are as follows:
φfi=1- φai (16)
Wherein, φfiFor i-th of T2It is worth corresponding absorption water saturation, %.
2. shale hole water adsorption amount according to claim 1, free amount and its evaluation method of distribution, feature exist
In shale core is saturated 24~48h of distilled water at 20 °C in step 1.
3. shale hole water adsorption amount, free amount described in -5 any one and its evaluation method of distribution according to claim 1,
It is characterized in that, shale core drying condition is dried for 24 hours under the conditions of being 110 DEG C in step 1.
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