Method and system for predicting water flooding recovery of fault block reservoirs considering whole process optimization

A system for predicting water flooding recovery of fault block reservoirs considering a whole process optimization, comprising:

• a fault block reservoir water flooding recovery influencing factor determining circuit, configured to:
• determine influencing factors in water flooding recovery of fault block reservoirs, and specifically configured to:
• collect geological information of fault block reservoirs in a target block, determine reservoir static physical parameters and production dynamic parameters in combination with field production data, and determine fault block characteristic parameters affecting water flooding recovery of the fault block reservoirs based on fault block reservoir characteristics and actual development of the reservoirs;
• a fault block reservoir water flooding recovery master parameter screening circuit, configured to:
• screen master parameters of the water flooding recovery of the fault block reservoir, and specifically configured to:
• change values of each of the influencing factors using single-factor analysis method, calculate the water flooding recovery of the fault block reservoirs by using numerical simulators of water flooding, analyze significance of the influencing factors with a variance D as an evaluating criterion for primary and secondary influencing factors, wherein the greater the variance D is, the higher the significance of the influencing factors is, and select the influencing factors with variances greater than 1 as master parameters of the water flooding recovery of the fault block reservoirs;
• a fault block reservoir water flooding recovery and master parameter single-factor correlation determining circuit, configured to:
• determine a single-factor correlation between the water flooding recovery of the fault block reservoirs and the master parameters, and specifically configured to:
• determine a correlation between the water flooding recovery of the fault block reservoirs and each of the master parameters using non-linear regression method, wherein the correlation comprises power function relationship, logarithmic function relationship, and polynomial function relationship;
• a multi-factor orthogonal experimental scheme designing circuit, configured to:
• design multi-factor orthogonal experimental schemes based on the master parameters, specifically configured to:
• determine the number of levels and values of each of the master parameters in combination with allowable range of parameters in fault block reservoir field, and select an orthogonal experimental design table, and further specifically configured to:
• firstly, determine the upper and lower limits of values of parameters required for orthogonal experiment analysis based on distribution intervals of the reservoir static physical parameters and fault block characteristic parameters determined in step (1) obtained from field tests;
• secondly, determine the upper and lower limits of values of the required production dynamic parameters according to distribution intervals of the production dynamic parameter used in developed reservoirs of the same type, take several levels for each of the parameters in the orthogonal experiment analysis, and uniformly sample values of each of the levels between the upper and lower limits of the values of each of the parameters;
• and
• finally, determine the orthogonal experimental design table and compile the multi-factor orthogonal experimental schemes according to the determined number of the master parameters and several values of the levels of each of the parameters;
• an experimental scheme whole-process water flooding optimizing circuit, configured to:
• perform a whole-process water flooding optimization for each of the experimental schemes, specifically configured to:
• with the maximum water flooding recovery as a target, optimize separate-layer injection and production at the moment of production, optimize well-type conversion when comprehensive water cut of the reservoirs reaches 90%, and optimize injection and production adjustment when the comprehensive water cut of the reservoirs reaches 95%, and further specifically configured to:
• divide multi-layer reservoirs into two sets of layer series of development longitudinally when water flooding is put into production according to the orthogonal experimental schemes for each of the fault block reservoirs, and specifically, calculate different combinations of the multi-layer reservoirs by using numerical simulators of water flooding reservoirs, wherein the combination of the multi-layer reservoirs corresponding to the scheme with the maximum water flooding recovery is a preferred implementation of the separate-layer injection and production;
• converse producing wells into water injection wells every other well when the comprehensive water cut of the reservoirs reaches 90%, that is, converse the original line of producing wells into the producing wells and the water injection wells arranged alternately;
• and
• calculate injection rates of each of the water injection wells and liquid producing rates of each of the producing wells as adjustable variables by using the numerical simulators of water flooding reservoirs when the comprehensive water cut of the reservoirs reaches 95%, wherein the combination of the injection rates of each of the water injection wells and the liquid producing rates of each of the producing wells corresponding to the scheme with the maximum water flooding recovery is a preferred injection and production scheme;
• a fault block reservoir water flooding recovery prediction model establishing circuit, configured to:
• establish a prediction model for the water flooding recovery of the fault block reservoirs, and specifically configured to:
• determine a formula of a correlation model of the water flooding recovery of the fault block reservoirs and all the master parameters according to the determined single-factor correlation between the water flooding recovery and the master parameters, determine unknown parameters of the formula of the correlation model of the water flooding recovery of the fault block reservoirs and all the master parameters using least square fitting method based on results of the whole process optimization of orthogonal experiments, and further obtain a prediction model for the water flooding recovery of the fault block reservoirs,
• the correlation model of the water flooding recovery of the fault block reservoirs and all the master parameters being shown in formula (V):
• R
• =
• a
• 1
• ⁢
• ln
• ⁢
• (
• A
• )
• +
• a
• 2
• ⁢
• log
• ⁢
• (
• PV
• )
• +
• a
• 3
• ⁢
• ln
• ⁢
• (
• μ
• o
• )
• +
• a
• 4
• (
• d
• f
• )
• +
• a
• 5
• ⁢
• k
• b
• +
• a
• 6
• ⁢
• V
• m
• c
• +
• a
• 7
• ⁢
• V
• r
• 2
• +
• a
• 8
• ⁢
• V
• r
• +
• a
• 9
• (
• V
• )
• where R represents the recovery, %;
• A represents the fault block area, km2;
• PV represents the production multiples;
• μo represents the underground crude oil viscosity, mPa·s;
• df represents the fault block density, block/km2;
• k represents the permeability, 10−3 μm2;
• Vm represents the inter-layer permeability ratio;
• Vr represents the variation coefficient of permeability;
• and an represents undetermined coefficient of the functional relationship with a subscript n=0, 1, 2, 3 . . . ;
• a fault block reservoir water flooding recovery calculating circuit, configured to:
• calculate the water flooding recovery of the fault block reservoirs according to the established prediction model for the water flooding recovery of the fault block reservoirs, and specifically configured to:
• calculate the water flooding recovery of the fault block reservoirs according to the established prediction model for the water flooding recovery of the fault block reservoirs;
• to compare the predicted water flooding recovery of the fault block reservoir calculated in step (7) with the current actual water flooding recovery of the fault block reservoir obtained in an oilfield;
• and
• determining a potential enhanced oil recovery by continuing water flooding for the fault block reservoir and exploiting crude oils.