Complex sentence: Within a year of the Doheny well there were 121 wells on the field interspersed with homes and businesses, and the field's cumulative production had reached 100,000 barrels; by 1897 the cumulative production had passed a million barrels, from 551 wells.
Split into simpler sentences: Within a year of the Doheny well there were 121 wells on the field interspersed with homes and businesses, and the field's cumulative production had reached 100,000 barrels. Cumulative production from the field at the end of that year had passed a million barrels, from 551 wells.