SUBROUTINE FormationInformationCalculator
    
    USE KickVariables
    Use TD_WellGeometry
    Use CReservoirVariables
    Use CFormationVariables
    USE Fluid_Flow_Startup_Vars
    USE CLog2
    USE CDownHoleVariables
    USE MudSystemVARIABLES
    

    IMPLICIT NONE
    
    INTEGER :: i
    REAL(8) :: WellGeoTopTVD
    
    KickGasType = 1             ! methane
    
!====================================================
!               Formation Length Calculation
!====================================================
    
    WellGeoTopTVD = 0.
    KickFormTopMD = 0.
    KickFormDownMD = 0.
    !===> Top Measured Depth of Formation
    Do i = 1 , TD_WellIntervalsCount
        if ( Reservoir%FormationTop >= TD_WellGeo(i)%VerticalDepth ) then
            KickFormTopMD = KickFormTopMD + TD_WellGeo(i)%IntervalLength
            !WRITE (*,*) ' here 11' , TD_WellGeo(i)%IntervalLength
            !WRITE (*,*) ' here v11' , TD_WellGeo(i)%VerticalDepth
            
            WellGeoTopTVD = TD_WellGeo(i)%VerticalDepth
        else if ( Reservoir%FormationTop < TD_WellGeo(i)%VerticalDepth ) then
            if ( TD_WellGeo(i)%HoleType == 0 ) then
                KickFormTopMD = KickFormTopMD + ((Reservoir%FormationTop - WellGeoTopTVD)&
                                / cos(TD_WellGeo(i)%StartAngle))
            !WRITE (*,*) ' here 12' , (FormationTop - WellGeoTopTVD) / cos(TD_WellGeo(i)%StartAngle)
                
            else
                KickFormTopMD = KickFormTopMD + (TD_WellGeo(i)%RCurvature &
                                * Asin((Reservoir%FormationTop - WellGeoTopTVD) / TD_WellGeo(i)%RCurvature))
            !WRITE (*,*) ' here 13' , TD_WellGeo(i)%RCurvature * Asin((FormationTop - WellGeoTopTVD) / TD_WellGeo(i)%RCurvature)
                
            end if
            exit
        end if
    End Do
    
    !!===> Down Measured Depth of Formation 
    WellGeoTopTVD = 0.
    Do i = 1 , TD_WellIntervalsCount
        if ( (Reservoir%FormationTop + Formation%Formations(Reservoir%FormationNo)%Thickness)>=TD_WellGeo(i)%VerticalDepth ) then
            KickFormDownMD = KickFormDownMD + TD_WellGeo(i)%IntervalLength
            WellGeoTopTVD = TD_WellGeo(i)%VerticalDepth
        else if ( (Reservoir%FormationTop+Formation%Formations(Reservoir%FormationNo)%Thickness)<TD_WellGeo(i)%VerticalDepth ) then
            if ( TD_WellGeo(i)%HoleType==0 ) then
                KickFormDownMD = KickFormDownMD + (((Reservoir%FormationTop+Formation%Formations(Reservoir%FormationNo)%Thickness)-WellGeoTopTVD)&
                                / cos(TD_WellGeo(i)%StartAngle)) 
            else
                KickFormDownMD = KickFormDownMD + (TD_WellGeo(i)%RCurvature &
                                * Asin((Reservoir%FormationTop - WellGeoTopTVD) / TD_WellGeo(i)%RCurvature))
            end if
            exit
        end if
    End Do
    
    !!===> Determination of Formation Length for Kick Modeling
    if (TD_WellTotalVerticalLength >= Reservoir%FormationTop .AND. TD_WellTotalVerticalLength < (Reservoir%FormationTop+Formation%Formations(Reservoir%FormationNo)%Thickness)) then
        KickFormLength = TD_WellTotalLength - KickFormTopMD   ![ft]
    else if ( TD_WellTotalVerticalLength >= (Reservoir%FormationTop + Formation%Formations(Reservoir%FormationNo)%Thickness) ) then
        KickFormLength = KickFormDownMD - KickFormTopMD       ![ft]
    else
        KickFormLength = 0.
    end if
    
    !PermeabilityExposedHeight = KickFormLength * FormationPermeability
    DownHole%PermeabilityExposedHeight = MudSystemDotFluidFlowCounter - MudSystemDotMudSys_timeCounter
!====================================================
!                Reservoir Data
!====================================================
    FormPermeability = Reservoir%FormationPermeability   ! [mD]
    
    FormPressure = TD_WellTotalVerticalLength * Formation%Formations(Reservoir%FormationNo)%PorePressureGradient          ![psia]
    DownHole%FormationPressure = INT(FormPressure)
    !CALL Log_2('FormPressure =' , FormPressure)
    !print*, 'Formations(FormationNo)%PorePressureGradient=', Formations(FormationNo)%PorePressureGradient
    !print * , 'FormationNo=' , FormationNo
    !print * , 'TD_WellTotalVerticalLength=' , TD_WellTotalVerticalLength
    FormTemperature = 600 ! [Ra]
    !WRITE (*,*) ' Formation pressure ' , FormPressure
    
    
!====================================================
!            Gas Properties (Methane Gas)
!====================================================
    
        GasResTemperature =  FormTemperature
        GasResPressure    =  FormPressure
    
        !!!! Methane , Gas type =1
        GasKickMolarMass = GasType(KickGasType)%MolarWt         ! Methane Gas [gr/mol]
        GasSpecGravity  = GasKickMolarMass / GasDensityRefrence
    
        KickTc = GasType(KickGasType)%CritTemp
        KickPc = GasType(KickGasType)%CritPress
    
        !!!!!!!! Calculating Compressibility, viscosity for influx condition (Average of reservoir and bottomhole)
        KickTr = GasResTemperature / KickTc
        KickPr = GasResPressure / KickPc
    
        K_A_Res = 3.53 * KickPr
        K_B_Res = 10.0**(0.9813 * KickTr)
        K_C_Res = 0.274 * (KickPr**2)
        K_D_Res = 10.0**(0.8157 * KickTr)
    
        GasResCompressibility = 0.98 !1. - (K_A_Res / K_B_Res) + (K_C_Res / K_D_Res)
        
        GasReservoirDensity = GasResPressure / (GasResCompressibility * &
                                GasResTemperature * GasType(KickGasType)%GasConstant) / Convft3toUSgal      ! [ppg]
            
END SUBROUTINE