| CPC G01V 11/002 (2013.01) [G01K 11/324 (2021.01); G01L 1/246 (2013.01); G01N 33/24 (2013.01)] | 3 Claims |
|
1. An evaluation method for relative contributions of heat sources based on helium, comprising a non-transitory computer readable medium operable on a computer with memory for the evaluation method for relative contributions of heat sources based on helium, and comprising program instructions for executing the following steps of:
Step 1: performing a geological survey to confirm the presence of deep channel communication generated in a study region in the context of major faulting and the presence of development and evolution of mud diapirs and upward migration of thermal fluid;
Step 2: collecting a sample from a reservoir of a typical well in the study region separating and purifying the sample;
Step 3: testing and analyzing the sample to obtain the content of CO2, 3He, and 4He;
Step 4: calculating 3He/enthalpy ratios of samples in different depths by a formula (1) and concentrations of CO2 and 3He of the samples, wherein the formula (1) is expressed in a dimensionless form, φ=f/(RT), which is divided into two parts, namely an ideal gas part φ° and a residual part φr, so φ:
 wherein δ=ρ/ρc, and τ=Tc/T; δ is a reduced density, and τ is a reversely reduced temperature; and ρ is a density under reservoir conditions of a stratum, and T is a temperature under the reservoir conditions of the stratum; and r is a residual value;
Step 5: using the following reference constants required by the formula (1):
Tc=647.096K;
ρc=322 kg m−3;
R=0.46151805 kJkg−1K−1 (2)-(4)
wherein Tc is a critical temperature, and ρc is a critical density;
Step 6: obtaining an equation of the ideal gas part φ° from a specific isobaric heat capacity equation
 in an ideal gas state:
 wherein the
 is fitted through a nonlinear least square method to determine coefficients b0 and bi and an index βi; let
 where i is an integer from 1 to 8,
 to simplify the formula; and ni° is a simplified coefficient, γi° is a simplified index, and the formula (5) is obtained;
Step 7: representing a form of the residual part φr as follows:
 wherein di, ti, αi, γi and ∈i are parameters; ψ is a special heat function, Δ is an arbitrary difference function, and ci is an index, and;
Step 8: calculating values of functions Δ, θ, and ψ of related nonanalytic terms:
Δ=θ2+Bi[(δ−1)2]ai
θ=(1−τ)+Ai[(δ−1)2]1/(2βi)
ψ=e−Ci(δ−1)2−Di(τ−1)2 (7)-(9)
wherein Ai, Bi, Ci, Di, and ai are introduced intrinsic parameters that are parameters of nonanalytic terms, which are included in nonlinear fitting of the whole equation, and θ is an adjustable parameter function;
Step 9: calculating an enthalpy value according to the following formula:
 wherein h is the enthalpy value, u is system inner energy, p is an external pressure, v is a system volume,
 is a first derivative of ϕ° with respect to τ,
 is a first derivative of ϕr with respect to τ, and
 is a first derivative of ϕr with respect to δ;
Step 10: assuming 3He/enthalpy ratios of mantle and crust thermal endmembers and estimating heat contributions of the mantle and the crust to a basin geothermal system according to a heat balance equation;
(3He/enthalpy)calculated=XM(3He/enthalpy)mantle+(1−XM)(3He/enthalpy)crust (13)
wherein XM is a mantle heat fraction in the sample, (3He/enthalpy)calculated is a 3He/enthalpy ratio calculated according to the formula (1), and (3He/enthalpy)mantle and (3He/enthalpy)crust respectively represent 3He/enthalpy ratios of mantle and crust thermal endmembers;
Step 11: determining a calculated mantle heat fraction as the relative heat contribution of the mantle to the basin geothermal system, the remaining contribution to the basin geothermal system coming from crust, a sum of contribution proportions of the two sources being 100%, the calculated mantle heat fraction indicating the contribution proportion of the mantle, and the remaining proportion indicating the contribution proportion of the crust; and
Step 12: optimizing a drilling path based on results of the evaluation method for relative contributions of heat sources based on helium which provides a reliable resource exploitation and reduces exploration risks.
|