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Merge pull request #3810 from totto82/refactor_bhpFromThpLimit_1

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Refactor bhp from thp limit
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Tor Harald Sandve 2022-03-22 13:57:52 +01:00 committed by GitHub
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6 changed files with 384 additions and 464 deletions
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279
opm/simulators/wells/MultisegmentWellGeneric.cpp
View File

@ -447,284 +447,7 @@ computeBhpAtThpLimitProdWithAlq(
DeferredLogger& deferred_logger,
double alq_value) const
{
// Given a VFP function returning bhp as a function of phase
// rates and thp:
// fbhp(rates, thp),
// a function extracting the particular flow rate used for VFP
// lookups:
// flo(rates)
// and the inflow function (assuming the reservoir is fixed):
// frates(bhp)
// we want to solve the equation:
// fbhp(frates(bhp, thplimit)) - bhp = 0
// for bhp.
//
// This may result in 0, 1 or 2 solutions. If two solutions,
// the one corresponding to the lowest bhp (and therefore
// highest rate) should be returned.
static constexpr int Water = BlackoilPhases::Aqua;
static constexpr int Oil = BlackoilPhases::Liquid;
static constexpr int Gas = BlackoilPhases::Vapour;
// Make the fbhp() function.
const auto& controls = baseif_.wellEcl().productionControls(summary_state);
const auto& table = baseif_.vfpProperties()->getProd()->getTable(controls.vfp_table_number);
const double vfp_ref_depth = table.getDatumDepth();
const double thp_limit = baseif_.getTHPConstraint(summary_state);
const double dp = wellhelpers::computeHydrostaticCorrection(baseif_.refDepth(), vfp_ref_depth, rho, baseif_.gravity());
auto fbhp = [this, &controls, thp_limit, dp, alq_value](
const std::vector<double>& rates) {
assert(rates.size() == 3);
return baseif_.vfpProperties()->getProd()
->bhp(controls.vfp_table_number, rates[Water], rates[Oil], rates[Gas], thp_limit, alq_value) - dp;
};
// Make the flo() function.
auto flo = [&table](const std::vector<double>& rates) {
return detail::getFlo(table, rates[Water], rates[Oil], rates[Gas]);
};
// Find the bhp-point where production becomes nonzero.
auto fflo = [&flo, &frates](double bhp) { return flo(frates(bhp)); };
auto bhp_max = this->bhpMax(fflo, controls.bhp_limit, maxPerfPress, table.getFloAxis().front(), deferred_logger);
// could not solve for the bhp-point, we could not continue to find the bhp
if (!bhp_max.has_value()) {
deferred_logger.warning("FAILED_ROBUST_BHP_THP_SOLVE_INOPERABLE",
"Robust bhp(thp) solve failed due to not being able to "
"find bhp-point where production becomes non-zero for well " + baseif_.name());
return std::nullopt;
}
// Define the equation we want to solve.
auto eq = [&fbhp, &frates](double bhp) {
return fbhp(frates(bhp)) - bhp;
};
// Find appropriate brackets for the solution.
const std::array<double, 2> range {controls.bhp_limit, *bhp_max};
std::optional<double> approximate_solution;
double low, high;
// trying to use bisect way to locate a bracket
bool finding_bracket = this->bisectBracket(eq, range, low, high, approximate_solution, deferred_logger);
// based on the origional design, if an approximate solution is suggested, we use this value directly
// in the long run, we might change it
if (approximate_solution.has_value()) {
return *approximate_solution;
}
if (!finding_bracket) {
deferred_logger.debug(" Trying the brute force search to bracket the bhp for last attempt ");
finding_bracket = this->bruteForceBracket(eq, range, low, high, deferred_logger);
}
if (!finding_bracket) {
deferred_logger.warning("FAILED_ROBUST_BHP_THP_SOLVE_INOPERABLE",
"Robust bhp(thp) solve failed due to not being able to "
"bracket the bhp solution with the brute force search for " + baseif_.name());
return std::nullopt;
}
// Solve for the proper solution in the given interval.
const int max_iteration = 100;
const double bhp_tolerance = 0.01 * unit::barsa;
int iteration = 0;
try {
const double solved_bhp = RegulaFalsiBisection<ThrowOnError>::
solve(eq, low, high, max_iteration, bhp_tolerance, iteration);
return solved_bhp;
}
catch (...) {
deferred_logger.warning("FAILED_ROBUST_BHP_THP_SOLVE",
"Robust bhp(thp) solve failed for well " + baseif_.name());
return std::nullopt;
}
}
template<typename Scalar>
std::optional<double>
MultisegmentWellGeneric<Scalar>::
bhpMax(const std::function<double(const double)>& fflo,
const double bhp_limit,
const double maxPerfPress,
const double vfp_flo_front,
DeferredLogger& deferred_logger) const
{
// Find the bhp-point where production becomes nonzero.
double bhp_max = 0.0;
double low = bhp_limit;
double high = maxPerfPress + 1.0 * unit::barsa;
double f_low = fflo(low);
double f_high = fflo(high);
deferred_logger.debug("computeBhpAtThpLimitProd(): well = " + baseif_.name() +
" low = " + std::to_string(low) +
" high = " + std::to_string(high) +
" f(low) = " + std::to_string(f_low) +
" f(high) = " + std::to_string(f_high));
int adjustments = 0;
const int max_adjustments = 10;
const double adjust_amount = 5.0 * unit::barsa;
while (f_low * f_high > 0.0 && adjustments < max_adjustments) {
// Same sign, adjust high to see if we can flip it.
high += adjust_amount;
f_high = fflo(high);
++adjustments;
}
if (f_low * f_high > 0.0) {
if (f_low > 0.0) {
// Even at the BHP limit, we are injecting.
// There will be no solution here, return an
// empty optional.
deferred_logger.warning("FAILED_ROBUST_BHP_THP_SOLVE_INOPERABLE",
"Robust bhp(thp) solve failed due to inoperability for well " + baseif_.name());
return std::nullopt;
} else {
// Still producing, even at high bhp.
assert(f_high < 0.0);
bhp_max = high;
}
} else {
// Bisect to find a bhp point where we produce, but
// not a large amount ('eps' below).
const double eps = 0.1 * std::fabs(vfp_flo_front);
const int maxit = 50;
int it = 0;
while (std::fabs(f_low) > eps && it < maxit) {
const double curr = 0.5*(low + high);
const double f_curr = fflo(curr);
if (f_curr * f_low > 0.0) {
low = curr;
f_low = f_curr;
} else {
high = curr;
f_high = f_curr;
}
++it;
}
if (it < maxit) {
bhp_max = low;
} else {
deferred_logger.warning("FAILED_ROBUST_BHP_THP_SOLVE_INOPERABLE",
"Bisect did not find the bhp-point where we produce for well " + baseif_.name());
return std::nullopt;
}
}
deferred_logger.debug("computeBhpAtThpLimitProd(): well = " + baseif_.name() +
" low = " + std::to_string(low) +
" high = " + std::to_string(high) +
" f(low) = " + std::to_string(f_low) +
" f(high) = " + std::to_string(f_high) +
" bhp_max = " + std::to_string(bhp_max));
return bhp_max;
}
template<typename Scalar>
bool
MultisegmentWellGeneric<Scalar>::
bisectBracket(const std::function<double(const double)>& eq,
const std::array<double, 2>& range,
double& low, double& high,
std::optional<double>& approximate_solution,
DeferredLogger& deferred_logger) const
{
bool finding_bracket = false;
low = range[0];
high = range[1];
double eq_high = eq(high);
double eq_low = eq(low);
const double eq_bhplimit = eq_low;
deferred_logger.debug("computeBhpAtThpLimitProd(): well = " + baseif_.name() +
" low = " + std::to_string(low) +
" high = " + std::to_string(high) +
" eq(low) = " + std::to_string(eq_low) +
" eq(high) = " + std::to_string(eq_high));
if (eq_low * eq_high > 0.0) {
// Failed to bracket the zero.
// If this is due to having two solutions, bisect until bracketed.
double abs_low = std::fabs(eq_low);
double abs_high = std::fabs(eq_high);
int bracket_attempts = 0;
const int max_bracket_attempts = 20;
double interval = high - low;
const double min_interval = 1.0 * unit::barsa;
while (eq_low * eq_high > 0.0 && bracket_attempts < max_bracket_attempts && interval > min_interval) {
if (abs_high < abs_low) {
low = 0.5 * (low + high);
eq_low = eq(low);
abs_low = std::fabs(eq_low);
} else {
high = 0.5 * (low + high);
eq_high = eq(high);
abs_high = std::fabs(eq_high);
}
++bracket_attempts;
}
if (eq_low * eq_high <= 0.) {
// We have a bracket!
finding_bracket = true;
// Now, see if (bhplimit, low) is a bracket in addition to (low, high).
// If so, that is the bracket we shall use, choosing the solution with the
// highest flow.
if (eq_low * eq_bhplimit <= 0.0) {
high = low;
low = range[0];
}
} else { // eq_low * eq_high > 0.0
// Still failed bracketing!
const double limit = 3.0 * unit::barsa;
if (std::min(abs_low, abs_high) < limit) {
// Return the least bad solution if less off than 3 bar.
deferred_logger.warning("FAILED_ROBUST_BHP_THP_SOLVE_BRACKETING_FAILURE",
"Robust bhp(thp) not solved precisely for well " + baseif_.name());
approximate_solution = abs_low < abs_high ? low : high;
} else {
// Return failure.
deferred_logger.warning("FAILED_ROBUST_BHP_THP_SOLVE_BRACKETING_FAILURE",
"Robust bhp(thp) solve failed due to bracketing failure for well " +
baseif_.name());
}
}
} else {
finding_bracket = true;
}
return finding_bracket;
}
template<typename Scalar>
bool
MultisegmentWellGeneric<Scalar>::
bruteForceBracket(const std::function<double(const double)>& eq,
const std::array<double, 2>& range,
double& low, double& high,
DeferredLogger& deferred_logger) const
{
bool finding_bracket = false;
low = range[0];
high = range[1];
const int sample_number = 100;
const double interval = (high - low) / sample_number;
double eq_low = eq(low);
double eq_high;
for (int i = 0; i < sample_number + 1; ++i) {
high = range[0] + interval * i;
eq_high = eq(high);
if (eq_high * eq_low <= 0.) {
finding_bracket = true;
break;
}
low = high;
eq_low = eq_high;
}
if (finding_bracket) {
deferred_logger.debug(
" brute force solve found low " + std::to_string(low) + " with eq_low " + std::to_string(eq_low) +
" high " + std::to_string(high) + " with eq_high " + std::to_string(eq_high));
}
return finding_bracket;
return baseif_.computeBhpAtThpLimitProdCommon(frates, summary_state, maxPerfPress, rho, alq_value, deferred_logger);
}
template<typename Scalar>

186
opm/simulators/wells/StandardWellGeneric.cpp
View File

@ -199,192 +199,10 @@ StandardWellGeneric<Scalar>::
computeBhpAtThpLimitProdWithAlq(const std::function<std::vector<double>(const double)>& frates,
const SummaryState& summary_state,
DeferredLogger& deferred_logger,
double maxPerfPress,
double alq_value) const
{
// Given a VFP function returning bhp as a function of phase
// rates and thp:
// fbhp(rates, thp),
// a function extracting the particular flow rate used for VFP
// lookups:
// flo(rates)
// and the inflow function (assuming the reservoir is fixed):
// frates(bhp)
// we want to solve the equation:
// fbhp(frates(bhp, thplimit)) - bhp = 0
// for bhp.
//
// This may result in 0, 1 or 2 solutions. If two solutions,
// the one corresponding to the lowest bhp (and therefore
// highest rate) is returned.
//
// In order to detect these situations, we will find piecewise
// linear approximations both to the inverse of the frates
// function and to the fbhp function.
//
// We first take the FLO sample points of the VFP curve, and
// find the corresponding bhp values by solving the equation:
// flo(frates(bhp)) - flo_sample = 0
// for bhp, for each flo_sample. The resulting (flo_sample,
// bhp_sample) values give a piecewise linear approximation to
// the true inverse inflow function, at the same flo values as
// the VFP data.
//
// Then we extract a piecewise linear approximation from the
// multilinear fbhp() by evaluating it at the flo_sample
// points, with fractions given by the frates(bhp_sample)
// values.
//
// When we have both piecewise linear curves defined on the
// same flo_sample points, it is easy to distinguish between
// the 0, 1 or 2 solution cases, and obtain the right interval
// in which to solve for the solution we want (with highest
// flow in case of 2 solutions).
static constexpr int Water = BlackoilPhases::Aqua;
static constexpr int Oil = BlackoilPhases::Liquid;
static constexpr int Gas = BlackoilPhases::Vapour;
// Make the fbhp() function.
const auto& controls = baseif_.wellEcl().productionControls(summary_state);
const auto& table = baseif_.vfpProperties()->getProd()->getTable(controls.vfp_table_number);
const double vfp_ref_depth = table.getDatumDepth();
const double thp_limit = baseif_.getTHPConstraint(summary_state);
const double dp = wellhelpers::computeHydrostaticCorrection(baseif_.refDepth(), vfp_ref_depth, getRho(), baseif_.gravity());
auto fbhp = [this, &controls, thp_limit, dp, alq_value](const std::vector<double>& rates) {
assert(rates.size() == 3);
return baseif_.vfpProperties()->getProd()
->bhp(controls.vfp_table_number, rates[Water], rates[Oil], rates[Gas], thp_limit, alq_value) - dp;
};
// Make the flo() function.
auto flo = [&table](const std::vector<double>& rates) {
return detail::getFlo(table, rates[Water], rates[Oil], rates[Gas]);
};
// Get the flo samples, add extra samples at low rates and bhp
// limit point if necessary. Then the sign must be flipped
// since the VFP code expects that production flo values are
// negative.
std::vector<double> flo_samples = table.getFloAxis();
if (flo_samples[0] > 0.0) {
const double f0 = flo_samples[0];
flo_samples.insert(flo_samples.begin(), { f0/20.0, f0/10.0, f0/5.0, f0/2.0 });
}
const double flo_bhp_limit = -flo(frates(controls.bhp_limit));
if (flo_samples.back() < flo_bhp_limit) {
flo_samples.push_back(flo_bhp_limit);
}
for (double& x : flo_samples) {
x = -x;
}
// Find bhp values for inflow relation corresponding to flo samples.
std::vector<double> bhp_samples;
for (double flo_sample : flo_samples) {
if (flo_sample < -flo_bhp_limit) {
// We would have to go under the bhp limit to obtain a
// flow of this magnitude. We associate all such flows
// with simply the bhp limit. The first one
// encountered is considered valid, the rest not. They
// are therefore skipped.
bhp_samples.push_back(controls.bhp_limit);
break;
}
auto eq = [&flo, &frates, flo_sample](double bhp) {
return flo(frates(bhp)) - flo_sample;
};
// TODO: replace hardcoded low/high limits.
const double low = 10.0 * unit::barsa;
const double high = 600.0 * unit::barsa;
const int max_iteration = 50;
const double flo_tolerance = 1e-6 * std::fabs(flo_samples.back());
int iteration = 0;
try {
const double solved_bhp = RegulaFalsiBisection<>::
solve(eq, low, high, max_iteration, flo_tolerance, iteration);
bhp_samples.push_back(solved_bhp);
}
catch (...) {
// Use previous value (or max value if at start) if we failed.
bhp_samples.push_back(bhp_samples.empty() ? high : bhp_samples.back());
deferred_logger.warning("FAILED_ROBUST_BHP_THP_SOLVE_EXTRACT_SAMPLES",
"Robust bhp(thp) solve failed extracting bhp values at flo samples for well " + baseif_.name());
}
}
// Find bhp values for VFP relation corresponding to flo samples.
const int num_samples = bhp_samples.size(); // Note that this can be smaller than flo_samples.size()
std::vector<double> fbhp_samples(num_samples);
for (int ii = 0; ii < num_samples; ++ii) {
fbhp_samples[ii] = fbhp(frates(bhp_samples[ii]));
}
// #define EXTRA_THP_DEBUGGING
#ifdef EXTRA_THP_DEBUGGING
std::string dbgmsg;
dbgmsg += "flo: ";
for (int ii = 0; ii < num_samples; ++ii) {
dbgmsg += " " + std::to_string(flo_samples[ii]);
}
dbgmsg += "\nbhp: ";
for (int ii = 0; ii < num_samples; ++ii) {
dbgmsg += " " + std::to_string(bhp_samples[ii]);
}
dbgmsg += "\nfbhp: ";
for (int ii = 0; ii < num_samples; ++ii) {
dbgmsg += " " + std::to_string(fbhp_samples[ii]);
}
OpmLog::debug(dbgmsg);
#endif // EXTRA_THP_DEBUGGING
// Look for sign changes for the (fbhp_samples - bhp_samples) piecewise linear curve.
// We only look at the valid
int sign_change_index = -1;
for (int ii = 0; ii < num_samples - 1; ++ii) {
const double curr = fbhp_samples[ii] - bhp_samples[ii];
const double next = fbhp_samples[ii + 1] - bhp_samples[ii + 1];
if (curr * next < 0.0) {
// Sign change in the [ii, ii + 1] interval.
sign_change_index = ii; // May overwrite, thereby choosing the highest-flo solution.
}
}
// Handle the no solution case.
if (sign_change_index == -1) {
return std::nullopt;
}
// Solve for the proper solution in the given interval.
auto eq = [&fbhp, &frates](double bhp) {
return fbhp(frates(bhp)) - bhp;
};
// TODO: replace hardcoded low/high limits.
const double low = bhp_samples[sign_change_index + 1];
const double high = bhp_samples[sign_change_index];
const int max_iteration = 50;
const double bhp_tolerance = 0.01 * unit::barsa;
int iteration = 0;
if (low == high) {
// We are in the high flow regime where the bhp_samples
// are all equal to the bhp_limit.
assert(low == controls.bhp_limit);
deferred_logger.warning("FAILED_ROBUST_BHP_THP_SOLVE",
"Robust bhp(thp) solve failed for well " + baseif_.name());
return std::nullopt;
}
try {
const double solved_bhp = RegulaFalsiBisection<>::
solve(eq, low, high, max_iteration, bhp_tolerance, iteration);
#ifdef EXTRA_THP_DEBUGGING
OpmLog::debug("***** " + name() + " solved_bhp = " + std::to_string(solved_bhp)
+ " flo_bhp_limit = " + std::to_string(flo_bhp_limit));
#endif // EXTRA_THP_DEBUGGING
return solved_bhp;
}
catch (...) {
deferred_logger.warning("FAILED_ROBUST_BHP_THP_SOLVE",
"Robust bhp(thp) solve failed for well " + baseif_.name());
return std::nullopt;
}
return baseif_.computeBhpAtThpLimitProdCommon(frates, summary_state, maxPerfPress, getRho(), alq_value, deferred_logger);
}
template<class Scalar>

1
opm/simulators/wells/StandardWellGeneric.hpp
View File

@ -105,6 +105,7 @@ protected:
std::optional<double> computeBhpAtThpLimitProdWithAlq(const std::function<std::vector<double>(const double)>& frates,
const SummaryState& summary_state,
DeferredLogger& deferred_logger,
double maxPerfPress,
double alq_value) const;
// Base interface reference

35
opm/simulators/wells/StandardWell_impl.hpp
View File

@ -2337,10 +2337,43 @@ namespace Opm
return rates;
};
return this->StandardWellGeneric<Scalar>::computeBhpAtThpLimitProdWithAlq(frates,
double max_pressure = 0.0;
for (int perf = 0; perf < this->number_of_perforations_; ++perf) {
const int cell_idx = this->well_cells_[perf];
const auto& int_quants = *(ebos_simulator.model().cachedIntensiveQuantities(cell_idx, /*timeIdx=*/ 0));
const auto& fs = int_quants.fluidState();
double pressure_cell = this->getPerfCellPressure(fs).value();
max_pressure = std::max(max_pressure, pressure_cell);
}
auto bhpAtLimit = this->StandardWellGeneric<Scalar>::computeBhpAtThpLimitProdWithAlq(frates,
summary_state,
deferred_logger,
max_pressure,
alq_value);
auto v = frates(*bhpAtLimit);
if(bhpAtLimit && std::all_of(v.cbegin(), v.cend(), [](double i){ return i <= 0; }))
return bhpAtLimit;
auto fratesIter = [this, &ebos_simulator, &deferred_logger](const double bhp) {
// Solver the well iterations to see if we are
// able to get a solution with an update
// solution
std::vector<double> rates(3);
computeWellRatesWithBhpIterations(ebos_simulator, bhp, rates, deferred_logger);
return rates;
};
bhpAtLimit = this->StandardWellGeneric<Scalar>::computeBhpAtThpLimitProdWithAlq(fratesIter,
summary_state,
deferred_logger,
max_pressure,
alq_value);
v = frates(*bhpAtLimit);
if(bhpAtLimit && std::all_of(v.cbegin(), v.cend(), [](double i){ return i <= 0; }))
return bhpAtLimit;
// we still don't get a valied solution.
return std::nullopt;
}

313
opm/simulators/wells/WellInterfaceGeneric.cpp
View File

@ -23,12 +23,14 @@
#include <opm/simulators/wells/WellInterfaceGeneric.hpp>
#include <opm/input/eclipse/Schedule/Well/WellTestState.hpp>
#include <opm/common/utility/numeric/RootFinders.hpp>
#include <opm/simulators/utils/DeferredLoggingErrorHelpers.hpp>
#include <opm/simulators/wells/PerforationData.hpp>
#include <opm/simulators/wells/ParallelWellInfo.hpp>
#include <opm/simulators/wells/VFPProperties.hpp>
#include <opm/simulators/wells/WellState.hpp>
#include <opm/simulators/wells/WellHelpers.hpp>
#include <opm/simulators/wells/VFPHelpers.hpp>
#include <cassert>
#include <cmath>
#include <cstddef>
@ -432,5 +434,314 @@ void WellInterfaceGeneric::reportWellSwitching(const SingleWellState& ws, Deferr
deferred_logger.info(msg);
}
std::optional<double>
WellInterfaceGeneric::
bhpMax(const std::function<double(const double)>& fflo,
const double bhp_limit,
const double maxPerfPress,
const double vfp_flo_front,
DeferredLogger& deferred_logger) const
{
// Find the bhp-point where production becomes nonzero.
double bhp_max = 0.0;
double low = bhp_limit;
double high = maxPerfPress + 1.0 * unit::barsa;
double f_low = fflo(low);
double f_high = fflo(high);
deferred_logger.debug("computeBhpAtThpLimitProd(): well = " + this->name() +
" low = " + std::to_string(low) +
" high = " + std::to_string(high) +
" f(low) = " + std::to_string(f_low) +
" f(high) = " + std::to_string(f_high));
int adjustments = 0;
const int max_adjustments = 10;
const double adjust_amount = 5.0 * unit::barsa;
while (f_low * f_high > 0.0 && adjustments < max_adjustments) {
// Same sign, adjust high to see if we can flip it.
high += adjust_amount;
f_high = fflo(high);
++adjustments;
}
if (f_low * f_high > 0.0) {
if (f_low > 0.0) {
// Even at the BHP limit, we are injecting.
// There will be no solution here, return an
// empty optional.
deferred_logger.warning("FAILED_ROBUST_BHP_THP_SOLVE_INOPERABLE",
"Robust bhp(thp) solve failed due to inoperability for well " + this->name());
return std::nullopt;
} else {
// Still producing, even at high bhp.
assert(f_high < 0.0);
bhp_max = high;
}
} else {
// Bisect to find a bhp point where we produce, but
// not a large amount ('eps' below).
const double eps = 0.1 * std::fabs(vfp_flo_front);
const int maxit = 50;
int it = 0;
while (std::fabs(f_low) > eps && it < maxit) {
const double curr = 0.5*(low + high);
const double f_curr = fflo(curr);
if (f_curr * f_low > 0.0) {
low = curr;
f_low = f_curr;
} else {
high = curr;
f_high = f_curr;
}
++it;
}
if (it < maxit) {
bhp_max = low;
} else {
deferred_logger.warning("FAILED_ROBUST_BHP_THP_SOLVE_INOPERABLE",
"Bisect did not find the bhp-point where we produce for well " + this->name());
return std::nullopt;
}
}
deferred_logger.debug("computeBhpAtThpLimitProd(): well = " + this->name() +
" low = " + std::to_string(low) +
" high = " + std::to_string(high) +
" f(low) = " + std::to_string(f_low) +
" f(high) = " + std::to_string(f_high) +
" bhp_max = " + std::to_string(bhp_max));
return bhp_max;
}
bool
WellInterfaceGeneric::
bisectBracket(const std::function<double(const double)>& eq,
const std::array<double, 2>& range,
double& low, double& high,
std::optional<double>& approximate_solution,
DeferredLogger& deferred_logger) const
{
bool finding_bracket = false;
low = range[0];
high = range[1];
double eq_high = eq(high);
double eq_low = eq(low);
const double eq_bhplimit = eq_low;
deferred_logger.debug("computeBhpAtThpLimitProd(): well = " + this->name() +
" low = " + std::to_string(low) +
" high = " + std::to_string(high) +
" eq(low) = " + std::to_string(eq_low) +
" eq(high) = " + std::to_string(eq_high));
if (eq_low * eq_high > 0.0) {
// Failed to bracket the zero.
// If this is due to having two solutions, bisect until bracketed.
double abs_low = std::fabs(eq_low);
double abs_high = std::fabs(eq_high);
int bracket_attempts = 0;
const int max_bracket_attempts = 20;
double interval = high - low;
const double min_interval = 1.0 * unit::barsa;
while (eq_low * eq_high > 0.0 && bracket_attempts < max_bracket_attempts && interval > min_interval) {
if (abs_high < abs_low) {
low = 0.5 * (low + high);
eq_low = eq(low);
abs_low = std::fabs(eq_low);
} else {
high = 0.5 * (low + high);
eq_high = eq(high);
abs_high = std::fabs(eq_high);
}
++bracket_attempts;
}
if (eq_low * eq_high <= 0.) {
// We have a bracket!
finding_bracket = true;
// Now, see if (bhplimit, low) is a bracket in addition to (low, high).
// If so, that is the bracket we shall use, choosing the solution with the
// highest flow.
if (eq_low * eq_bhplimit <= 0.0) {
high = low;
low = range[0];
}
} else { // eq_low * eq_high > 0.0
// Still failed bracketing!
const double limit = 3.0 * unit::barsa;
if (std::min(abs_low, abs_high) < limit) {
// Return the least bad solution if less off than 3 bar.
deferred_logger.warning("FAILED_ROBUST_BHP_THP_SOLVE_BRACKETING_FAILURE",
"Robust bhp(thp) not solved precisely for well " + this->name());
approximate_solution = abs_low < abs_high ? low : high;
} else {
// Return failure.
deferred_logger.warning("FAILED_ROBUST_BHP_THP_SOLVE_BRACKETING_FAILURE",
"Robust bhp(thp) solve failed due to bracketing failure for well " +
this->name());
}
}
} else {
finding_bracket = true;
}
return finding_bracket;
}
bool
WellInterfaceGeneric::
bruteForceBracket(const std::function<double(const double)>& eq,
const std::array<double, 2>& range,
double& low, double& high,
DeferredLogger& deferred_logger) const
{
bool finding_bracket = false;
low = range[0];
high = range[1];
const int sample_number = 100;
const double interval = (high - low) / sample_number;
double eq_low = eq(low);
double eq_high;
for (int i = 0; i < sample_number + 1; ++i) {
high = range[0] + interval * i;
eq_high = eq(high);
if (eq_high * eq_low <= 0.) {
finding_bracket = true;
break;
}
low = high;
eq_low = eq_high;
}
if (finding_bracket) {
deferred_logger.debug(
" brute force solve found low " + std::to_string(low) + " with eq_low " + std::to_string(eq_low) +
" high " + std::to_string(high) + " with eq_high " + std::to_string(eq_high));
}
return finding_bracket;
}
std::optional<double>
WellInterfaceGeneric::
computeBhpAtThpLimitProdCommon(const std::function<std::vector<double>(const double)>& frates,
const SummaryState& summary_state,
const double maxPerfPress,
const double rho,
const double alq_value,
DeferredLogger& deferred_logger) const
{
// Given a VFP function returning bhp as a function of phase
// rates and thp:
// fbhp(rates, thp),
// a function extracting the particular flow rate used for VFP
// lookups:
// flo(rates)
// and the inflow function (assuming the reservoir is fixed):
// frates(bhp)
// we want to solve the equation:
// fbhp(frates(bhp, thplimit)) - bhp = 0
// for bhp.
//
// This may result in 0, 1 or 2 solutions. If two solutions,
// the one corresponding to the lowest bhp (and therefore
// highest rate) should be returned.
static constexpr int Water = BlackoilPhases::Aqua;
static constexpr int Oil = BlackoilPhases::Liquid;
static constexpr int Gas = BlackoilPhases::Vapour;
// Make the fbhp() function.
const auto& controls = this->wellEcl().productionControls(summary_state);
const auto& table = this->vfpProperties()->getProd()->getTable(controls.vfp_table_number);
const double vfp_ref_depth = table.getDatumDepth();
const double thp_limit = this->getTHPConstraint(summary_state);
const double dp = wellhelpers::computeHydrostaticCorrection(this->refDepth(), vfp_ref_depth, rho, this->gravity());
auto fbhp = [this, &controls, thp_limit, dp, alq_value](const std::vector<double>& rates) {
assert(rates.size() == 3);
return this->vfpProperties()->getProd()
->bhp(controls.vfp_table_number, rates[Water], rates[Oil], rates[Gas], thp_limit, alq_value) - dp;
};
// Make the flo() function.
auto flo = [&table](const std::vector<double>& rates) {
return detail::getFlo(table, rates[Water], rates[Oil], rates[Gas]);
};
// Find the bhp-point where production becomes nonzero.
auto fflo = [&flo, &frates](double bhp) { return flo(frates(bhp)); };
auto bhp_max = this->bhpMax(fflo, controls.bhp_limit, maxPerfPress, table.getFloAxis().front(), deferred_logger);
// could not solve for the bhp-point, we could not continue to find the bhp
if (!bhp_max.has_value()) {
deferred_logger.warning("FAILED_ROBUST_BHP_THP_SOLVE_INOPERABLE",
"Robust bhp(thp) solve failed due to not being able to "
"find bhp-point where production becomes non-zero for well " + this->name());
return std::nullopt;
}
const std::array<double, 2> range {controls.bhp_limit, *bhp_max};
return computeBhpAtThpLimitCommon(frates, fbhp, range, deferred_logger);
}
std::optional<double>
WellInterfaceGeneric::
computeBhpAtThpLimitCommon(const std::function<std::vector<double>(const double)>& frates,
const std::function<double(const std::vector<double>)>& fbhp,
const std::array<double, 2>& range,
DeferredLogger& deferred_logger) const
{
// Given a VFP function returning bhp as a function of phase
// rates and thp:
// fbhp(rates, thp),
// a function extracting the particular flow rate used for VFP
// lookups:
// flo(rates)
// and the inflow function (assuming the reservoir is fixed):
// frates(bhp)
// we want to solve the equation:
// fbhp(frates(bhp, thplimit)) - bhp = 0
// for bhp.
//
// This may result in 0, 1 or 2 solutions. If two solutions,
// the one corresponding to the lowest bhp (and therefore
// highest rate) should be returned.
// Define the equation we want to solve.
auto eq = [&fbhp, &frates](double bhp) {
return fbhp(frates(bhp)) - bhp;
};
// Find appropriate brackets for the solution.
std::optional<double> approximate_solution;
double low, high;
// trying to use bisect way to locate a bracket
bool finding_bracket = this->bisectBracket(eq, range, low, high, approximate_solution, deferred_logger);
// based on the origional design, if an approximate solution is suggested, we use this value directly
// in the long run, we might change it
if (approximate_solution.has_value()) {
return *approximate_solution;
}
if (!finding_bracket) {
deferred_logger.debug(" Trying the brute force search to bracket the bhp for last attempt ");
finding_bracket = this->bruteForceBracket(eq, range, low, high, deferred_logger);
}
if (!finding_bracket) {
deferred_logger.warning("FAILED_ROBUST_BHP_THP_SOLVE_INOPERABLE",
"Robust bhp(thp) solve failed due to not being able to "
"bracket the bhp solution with the brute force search for " + this->name());
return std::nullopt;
}
// Solve for the proper solution in the given interval.
const int max_iteration = 100;
const double bhp_tolerance = 0.01 * unit::barsa;
int iteration = 0;
try {
const double solved_bhp = RegulaFalsiBisection<ThrowOnError>::
solve(eq, low, high, max_iteration, bhp_tolerance, iteration);
return solved_bhp;
}
catch (...) {
deferred_logger.warning("FAILED_ROBUST_BHP_THP_SOLVE",
"Robust bhp(thp) solve failed for well " + this->name());
return std::nullopt;
}
}
} // namespace Opm

34
opm/simulators/wells/WellInterfaceGeneric.hpp
View File

@ -179,6 +179,16 @@ public:
bool changedToOpenThisStep() const {
return this->changed_to_open_this_step_;
}
std::optional<double> computeBhpAtThpLimitProdCommon(const std::function<std::vector<double>(const double)>& frates,
const SummaryState& summary_state,
const double maxPerfPress,
const double rho,
const double alq_value,
DeferredLogger& deferred_logger
) const;
protected:
bool getAllowCrossFlow() const;
double mostStrictBhpFromBhpLimits(const SummaryState& summaryState) const;
@ -187,6 +197,30 @@ protected:
WellTestState& well_test_state,
DeferredLogger& deferred_logger) const;
std::optional<double> bhpMax(const std::function<double(const double)>& fflo,
const double bhp_limit,
const double maxPerfPress,
const double vfp_flo_front,
DeferredLogger& deferred_logger) const;
std::optional<double> computeBhpAtThpLimitCommon(
const std::function<std::vector<double>(const double)>& frates,
const std::function<double(const std::vector<double>)>& fbhp,
const std::array<double, 2>& range,
DeferredLogger& deferred_logger) const;
bool bruteForceBracket(const std::function<double(const double)>& eq,
const std::array<double, 2>& range,
double& low, double& high,
DeferredLogger& deferred_logger) const;
bool bisectBracket(const std::function<double(const double)>& eq,
const std::array<double, 2>& range,
double& low, double& high,
std::optional<double>& approximate_solution,
DeferredLogger& deferred_logger) const;
// definition of the struct OperabilityStatus
struct OperabilityStatus {