SQL & PL/SQL :: Function BFILENAME() Usage?

I had a question on BFILENAME() :
first,

create or replace directory UTL_FILE_DIR as 'k:lob_test';
GRANT READ,WRITE ON DIRECTORY UTL_FILE_DIR TO user1;

and then ,I login use user : user1

create or replace package body p_utl_mail_attach_raw as
procedure send_single_user_attach_raw(........)
fil BFILE;
filenm VARCHAR2(50) := 'aaa.jpg'
begin
fil := BFILENAME('UTL_FILE_DIR', filenm);
end ;

this result it show :
UTL_FILE_DIR/aaa.jpg, exists=F, length=0, open=F