Pemetaan distribusi porositas dengan kontrol impedansi akustik menggunakan metode sequential gaussian simulation (SGS) : studi kasus formasi Baturaja, Lapangan Krisna, Cekungan Sunda = Porosity distribution mapping controlled with acoustic impedance used Sequential Gaussian Simulation (SGS) method : a study case at Baturaja formation, Krisna Field, Sunda Basin