CN103577886A - Staged fracturing yield prediction method of low-permeability gas reservoir horizontal well - Google Patents

Abstract

The invention provides a staged fracturing yield prediction method of a low-permeability gas reservoir horizontal well, and belongs to the fracturing field of the low-permeability gas reservoir horizontal well in development of oil-gas fields. According to the method, horizontal well fracturing design is firstly carried out to obtain original data, then geological modeling is carried out according to the original data to obtain a geological model, finally area network refinement and fracturing crack simulation are carried out on the geological model, and therefore the yield of the horizontal well under different crack parameters is calculated. By combing FracProPT2007 and Eclipse, the staged fracturing yield prediction method of the low-permeability gas reservoir horizontal well can accurately capture the shapes of fracture cracks and flowing parameters of the fracture cracks in each position, can simulate the flowing of multi-layer and multi-phase fluid flowing into the cracks and flowing into a shaft from the cracks, and analyzes the influence of the geometic shapes of the cracks, the flow guide capacity, the crack positions, the interval, the included angle of the cracks, the base material permeability and other parameters on yield, and leakage of fracturing liquid and the flow-back process of the fracturing liquid are taken into account.

Description

A kind of low permeability gas reservoirs staged fracturing of horizontal well PRODUCTION FORECASTING METHODS

Technical field

The invention belongs to the low permeability gas reservoir fractured horizontal well field in oil-gas field development, be specifically related to a kind of low permeability gas reservoirs staged fracturing of horizontal well PRODUCTION FORECASTING METHODS, for FRACTURING DESIGN provides effective guidance.

Background technology

In recent years, along with the progress of drilling technique and the continuous reduction of drilling cost, the Oil Reservoir Types of horizontal well application is more and more extensive, become LOW PERMEABILITY RESERVOIR conversion development scheme, improve the effective means of recovery ratio, along with horizontal well technology and Fracturing Technology constantly improve and ripe, fracturing technique is applied to horizontal wells field and become new research direction of horizontal wells technology, in low-permeability oil gas reservoir, to fractured horizontal well, to obtain higher yield, be the milestone that low-permeability oil gas field is developed, Given this, staged fracturing of horizontal well capability forecasting technology more and more embodies its necessity accurately.

At present, staged fracturing of horizontal well capability forecasting mainly comprises analytic method capability forecasting, semi-analytic method capability forecasting and conventional numerical simulation PRODUCTION FORECASTING METHODS.

Wherein, analytic method is the deduce mathematical based on strict generally, and the expression formula form obtaining is comparatively simple.But analytic method has comparatively harsh assumed condition, is difficult in actual applications be met.Generally, the method is used for simple forecast and the evaluation of fractured horizontal well's productivity.

Semi-analytic method can solve and become at any angle bidimensional or three-dimensional cracking to cross the capability forecasting problem of water horizontal well with pit shaft, and takes into full account the impact on fractured well production capacity of Reservoir Heterogeneity and the dissimilar border of oil reservoir.In low-permeability oil deposit, consider the impact of non-Darcy effect on production capacity, can be by the matching of adjacent fractured horizontal well's productivity being carried out to the indivedual parameters in correction model, and the recovery prediction that fitting result is applied to other pressure break horizontal well of same block is to improve computational accuracy, but semi-analytic method can only solve single-phase problem.

Numerical simulation can solve the problem of oil, gas, water three phase fluid flow, for the productivity simulation under the various conditions of production of pressure break horizontal well, has irreplaceable advantage.For example applying Eclipse black-oil-type simulation model can dummy level well hydraulically created fracture, and calculate production capacity, but this method is extremely loaded down with trivial details, first want grid division to represent actual Fracture geometric size, also need in addition the various parameters in manual input crack, but each position permeability of crack, the parameters such as flow conductivity may be inputted hardly successively, can only average, and simulation process do not consider in fracturing process fracturing fluid leak injury and press after the row of returning, and these factors are particularly important to low permeability gas reservoirs, therefore so conventional method for numerical simulation is not combined closely with FRACTURING DESIGN, be difficult to represent that real crack attribute is also difficult to real reflection and presses rear gas generation process, therefore brought the inaccurate of capability forecasting result of calculation.

Summary of the invention

The object of the invention is to solve the difficult problem existing in above-mentioned prior art, a kind of low permeability gas reservoirs staged fracturing of horizontal well PRODUCTION FORECASTING METHODS is provided, can accurately catch fracturing fracture form and at its each diverse location place flow parameter, can simulate flowing of multilayer, polyphasic flow fluid inflow He Cong crack, crack inflow pit shaft, analyze the impacts of parameter on production capacity such as crack geometric shape, flow conductivity, crack location, spacing, crack angle, matrix permeability, and consider fracturing fluid leak and the row's of returning process thereof.

The present invention is achieved by the following technical solutions:

A kind of low permeability gas reservoirs staged fracturing of horizontal well PRODUCTION FORECASTING METHODS, first described method is carried out fractured horizontal well design and is obtained raw data, then according to described raw data, carry out Geologic modeling and obtain geologic model, finally by described geologic model is carried out area grid refinement and simulation fracturing fracture, thereby calculate the horizontal well production under different fracture parameters.

Said method comprising the steps of:

Step 1: utilize Fracturing design software to carry out fractured horizontal well design and obtain raw data, described raw data is stored in the oil reservoir digital-to-analogue file automatically being generated by Fracturing design software;

Step 2: described oil reservoir digital-to-analogue file is changed and generated the data file that can be identified by reservoir simulation software;

Step 3: utilize reservoir simulation software to carry out Geologic modeling and grid division: to import the data file that step 2 produces in reservoir simulation software, reservoir simulation software is by this data file automatic acquisition stratum and fracture parameters and stratum, crack of the fracturing fluid leak-off situation around, then select the black-oil-type simulation model module simulation calculated level well staged fracturing production capacity in reservoir simulation software, obtain the horizontal well production under different Number of Fractures;

Step 4: the fracture parameters in step 3 comprises geometric shape, number, spacing, angle, flow conductivity and crack location, by analyzing different fracture parameters and matrix, production capacity is affected, change the value of a parameter in fracture parameters, and the basic value of other parameter remains unchanged, calculated level well staged fracturing production capacity, finally determines optimum fracture length respectively.

Compared with prior art, the invention has the beneficial effects as follows: utilize the inventive method can accurately catch fracturing fracture form and at its each diverse location place flow parameter, can simulate flowing of multilayer, polyphasic flow fluid inflow He Cong crack, crack inflow pit shaft, analyze the impacts of parameter on production capacity such as crack geometric shape, flow conductivity, crack location, spacing, crack angle, matrix permeability, and wherein considered fracturing fluid leak and the row's of returning process thereof, this is particularly important to the prediction of low permeability reservoirs productivity of fractured horizontal well.

Accompanying drawing explanation

Fig. 1 is the step block diagram of low permeability gas reservoirs staged fracturing of horizontal well PRODUCTION FORECASTING METHODS of the present invention.

Fig. 2 is the permeability at the diverse location place, crack in the embodiment of the present invention.

Fig. 3 is that the Local grid of the simulation fracture in the embodiment of the present invention is divided.

Fig. 4 is the DP1 horizontal well actual measurement output in the embodiment of the present invention.

Fig. 5 is the DP1 horizontal well forecast production in the embodiment of the present invention.

Embodiment

Below in conjunction with accompanying drawing, the present invention is described in further detail:

The staged fracturing of horizontal well capability forecasting simulation method that the inventive method combines with reservoir simulation software (employing Eclipse) by Fracturing design software (adopt FracproPT2007) can accurately catch fracturing fracture form and at its each diverse location place flow parameter, its step as shown in Figure 1, comprising:

Step 1, in FracproPT2007, simulate hydraulically created fracture parameters (seam is long, it is wide to stitch, it is high to stitch and sanding concentration everywhere of crack, flow conductivity etc.), comprise the determining of reservoir description, perforation position and hole count, fracturing liquid, the selection of propping agent and the optimization of optimum infusion program of the determining of horizontal hole track, horizontal well payzone and upper and lower interlayer, thereby obtain the raw data associated consistent with infusion program, these raw data are stored in the automatic oil reservoir digital-to-analogue file generating of FracproPT2007; Described raw data comprises fracture length, fracture height, fracture width, fracture flow capacity and sanding concentration;

Step 2: by the data file of oil reservoir digital-to-analogue file generated Ke Bei Eclipse reservoir simulation software identification, be about in FRACTURING DESIGN results of fracture simulation result (seam is long, it is wide to stitch, it is high to stitch and sanding concentration everywhere of crack, flow conductivity etc.) input Eclipse geologic model by FracproPT2007 and Eclipse combination interface.Specifically, in the combobox in FracproPT2007 and the Eclipse combination interface lower right corner, there are various document format datas available, select Eclipse file, then click and generate button, generate and can be identified raw data file by Eclipse;

Fracture and periphery mesh refinement in step 3 ， Eclipse reservoir simulation software, accurately catch fracture morphology and flow at its each diverse location place.By area grid refinement, in reservoir simulation software, import the raw data file that previous step produces, can obtain each property parameters of stratum and fracturing fracture and stratum, crack of the fracturing fluid leak-off situation (meaning is that after input data file, Eclipse has obtained these parameters and leak-off situation automatically) around, and automatically carry out grid division (Fracturing design software is generating mesh dividing data automatically), for accurate analog result, refinement (in fracture software generating mesh data) can be carried out in crack around grid, in Eclipse, black-oil-type simulation model module can be simulated the seepage flow characteristics of the single-phase or multinomial stream under Different Strata condition, and then calculating Oil & Gas Productivity, therefore, select this black-oil-type simulation model module simulation calculated level well staged fracturing production capacity, select the black-oil-type simulation model module simulation calculated level well staged fracturing production capacity in reservoir simulation software (black-oil-type simulation model module to be inputted to well control area, reservoir limit situation, reservoir characteristics, fracture parameters, fluid behaviour and well manufacturing parameter, calculate production capacity.), obtain the horizontal well production under different Number of Fractures, realize low permeability gas reservoirs fractured horizontal well design optimization.

Step 4, analyzes different fracture parameters (geometric shape, number, spacing, angle and flow conductivity etc.) and the impact of matrix on production capacity.Change the value of one of them parameter, and the basic value of other parameter remains unchanged and carries out evaluating production capacity (in step 3, Eclipse obtains after FRACTURING DESIGN parameter, can design basic parameter, only change one of them parameter and other parameter constant, as only changed crack Number of Fractures, and other parameter constant of crack, the change of Number of Fractures can be in the input of associating software interface, and the change of other parameter can change when FRACTURING DESIGN, and generated data is identified by Eclipse), as get fracture length and be respectively 80m, 100m, 120m, 140m, 160m, 180m, other parameter value is constant, calculate respectively production capacity, determine optimum fracture length.

The inventive method is by crack and mesh refinement around thereof, can accurately catch fracture morphology and at the grid property at its each diverse location place (the fracture parameters numerical value of grid representative), and record of the fracturing fluid leak-off process (in step 3) in fracturing process, thereby be convenient to determine the original state of producing crack periphery while starting, also fracturing fluid leak and the row's of returning process thereof have been considered in i.e. this prediction, and this is particularly important to the prediction of low permeability reservoirs productivity of fractured horizontal well.

Utilize the present invention can simulate flowing of multilayer, polyphasic flow fluid inflow He Cong crack, crack inflow pit shaft, analyze the impacts of parameter on production capacity such as crack geometric shape, flow conductivity, crack location, spacing, crack angle, matrix permeability, and wherein considered fracturing fluid leak and the row's of returning process thereof, this is particularly important to the prediction of low permeability reservoirs productivity of fractured horizontal well.

Fig. 2 is the fracture permeability schematic diagram that utilizes the inventive method to obtain, as can be seen from Figure 2, by crack and mesh refinement around thereof, can accurately obtain the flow conductivity at each diverse location place, crack, this obviously tallies with the actual situation more than average fracture flow capacity method of traditional setting.

For accurate simulation matrix to crack, crack to pit shaft, fracture tip conflux and initial stage of production the instantaneous of two-forty flow, conventionally around needing fracture, grid carries out refinement (as shown in step 3), scope is that 1.5,2 times of (grid in Fig. 3 non-uniform Distribution) cracks are long respectively in X, Y-direction, as shown in Figure 3.

Eclipse can set the parameters such as different Number of Fractures, fracture length, kerf spacing, seam and horizontal segment root, toe distance and carry out production capacity calculating, and in simulation fracture process, consider non-Darcy Flow impact, analyze the impacts of parameter on production capacity such as crack geometric shape, flow conductivity, crack location, spacing, crack angle, matrix permeability.In multilayer situation, Eclipse reservoir simulation software also in the vertical each layer carry out grid division, simulation multilayer, multinomial flowing, therefore the method can be carried out multilayer, polyphasic flow staged fracturing of horizontal well capability forecasting, and this also at present separately application waterfrac treatment software prediction production capacity be difficult to accomplish.In simulation process, the available actual flaw size of the setting of fracture width, also can or dwindle its expansion, and prerequisite is to guarantee that fracture flow capacity is constant, and formula (1), (2) are corresponding conversion formula.

$k_f=k_{\mathrm{fi}}\frac{b}{\mathrm{\Δy}}---\left(1\right)$

${\mathrm{\φ}}_f={\mathrm{\φ}}_{\mathrm{fi}}\frac{b}{\mathrm{\Δy}}---\left(2\right)$

In above two formulas, k _ffor actual fracture permeability, k _fifor simulation fracture permeability, b is actual fracture width, and Δ y is simulation lattice width.

The oil reservoir digital-to-analogue file (above-mentioned all raw data are stored in this oil reservoir digital-to-analogue file) (grid assignment obtains after step 3 gridding) after grid assignment producing through FracProPT2007 mainly comprises PVT file, fluid properties file and output initialization reservoir fluid saturation degree file (utilize FracProPT2007 to produce oil reservoir digital-to-analogue file, then oil reservoir digital-to-analogue file is processed and is obtained this three files through Eclipse), remaining reservoir simulation file oozes curve S CAL file mutually as reservoir, horizontal well produces schedule file and other reservoir characteristics initial value file needs artificial input.

Certain gas field DP1 horizontal well is carried out to capability forecasting to be shown, with the production of this method prediction, after one month, stable rate is (as shown in Figure 5,40000m3/day) more meet pressure break after actual output (as shown in Figure 4,38000m3/day), and actual field is (25000m3/day) by the output of additive method prediction.

In recent years, adopt the method for the hypotonic oil gas field of horizontal well development more and more to come into one's own, 50000 mouthfuls of left and right of global current horizontal well sum, and Chinese nearly 2000 mouthfuls.According to the viewpoint of reservoir engineering, the contact area rate straight well of longer horizontal hole and oil reservoir is much bigger, tight stratum especially, and when the productivity index is lower, horizontal well is obviously better than straight well.Along with horizontal well technology and Fracturing Technology constantly improve and ripe, fracturing technique is applied to horizontal wells field and become new research direction of horizontal wells technology, therefore, staged fracturing of horizontal well capability forecasting can provide important information for on-the-spot FRACTURING DESIGN accurately, has broad application prospects.

Technique scheme is one embodiment of the present invention, for those skilled in the art, the invention discloses on the basis of application process and principle, be easy to make various types of improvement or distortion, and be not limited only to the described method of the above-mentioned embodiment of the present invention, therefore previously described mode is just preferred, and does not have restrictive meaning.

Claims (2)

1. a low permeability gas reservoirs staged fracturing of horizontal well PRODUCTION FORECASTING METHODS, it is characterized in that: first described method is carried out fractured horizontal well design and obtained raw data, then according to described raw data, carry out Geologic modeling and obtain geologic model, finally by described geologic model is carried out area grid refinement and simulation fracturing fracture, thereby calculate the horizontal well production under different fracture parameters.

2. low permeability gas reservoirs staged fracturing of horizontal well PRODUCTION FORECASTING METHODS according to claim 1, is characterized in that: said method comprising the steps of:

Said method comprising the steps of:

Step 1: utilize Fracturing design software to carry out fractured horizontal well design and obtain raw data, described raw data is stored in the oil reservoir digital-to-analogue file automatically being generated by Fracturing design software;

Step 2: described oil reservoir digital-to-analogue file is changed and generated the data file that can be identified by reservoir simulation software;

Step 3: utilize reservoir simulation software to carry out Geologic modeling and grid division: to import the data file that step 2 produces in reservoir simulation software, reservoir simulation software is by this data file automatic acquisition stratum and fracture parameters and stratum, crack of the fracturing fluid leak-off situation around, then select the black-oil-type simulation model module simulation calculated level well staged fracturing production capacity in reservoir simulation software, obtain the horizontal well production under different Number of Fractures;

Step 4: the fracture parameters in step 3 comprises geometric shape, number, spacing, angle, flow conductivity and crack location, by analyzing different fracture parameters and matrix, production capacity is affected, change the value of a parameter in fracture parameters, and the basic value of other parameter remains unchanged, calculated level well staged fracturing production capacity, finally determines optimum fracture length respectively.

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