[{"name":"a name","project":[{companyName:"a name",contactPerson:[{work_email:"test@test.com"}]},{companyName:"a name1",contactPerson:[{work_email:"test1@test.com"}]},{companyName:"a name2",contactPerson:[{work_email:"test2@test.com"}]},{companyName:"a name3",contactPerson:[{work_email:"test@test.com"}]},]}]

db.collection.find({"project.contactPerson.work_email":"test@test.com"},{"project.$":1})