Since 1993, Electrical Submergible Pumps (ESPs have been applied with excellent results in the cold production of heavy crudes (9.5 API) in about 70 horizontal wells in the hamaca area of the Orinoco Faja. Over the three year production life of these wells, production declinations due to natural and mechanical causes of up to 50 % have been observed.
As an alternative to increase the production to the original rate of around 1500 bpd, cyclical steam injection in conjunction with the ESPs has been proposed. This process will entail periodic injection of steam in vertical or deviated wells in the same reservoir as the horizontal wells in order to evaluate the performance of ESPs in the high temperature environment. This test will be conducted in the latter part of 1996 with the intention of applying the results to the horizontal wells during the fiscal year 1997.
The evaluation will be realized as a joint effort between CORPOVEN and CENTRILIFT as a part of their strategic alliance which is now in operation.
The technical paper will show the ESP designs, the evaluation program, and the results, while comparing the production rates and costs of cold vs. thermal production methods.
Heavy and extraheavy crude oil has traditionally. been produced in both cold and hot production (cyclic steam infection) with pumping units as the artificial lift method These pumping units have been replaced in part by electrical submersible pumps. (ESPS) Initially its application was in horizontal wells in the Orinoco Belt extending this system to the traditional areas of heavy oil. Right now, there are more than eighty wells producing more than 50,000 bpd in cold production with ESPS.
The outcome obtained with the application of ESPS have been excellent. Rates per well of over 2,500 bpd (16.6 m3 /h) of 9.1 API of crude oil have been recorded; however, some of the horizontal wells did not perform as expected, due to formation damage caused by drilling fluids during the completion of the wells.
As a result, the action taken was to stimulate these low productivity wells. The first stimulations were chemical (HCL), getting initially good results by increasing the production of the well from 150–200 bpd (0.99–1.32 m3 /h) to 800 bpd (5.29m3 /h). This production lasted one to two months. The other stimulation applied was thermal (cyclic steam stimulation); the first test was made in the well FBA 18 from the Bare field of the Orinoco Belt. This well incremented its production from 150 bpd (0.99 m3 /h) to 900 bpd (5.96 m3 /h), keeping the same rate for four months (until the writing of this paper). This well started to produce with an ESP system and continued to produce with the same method specially suited for thermal operations.
The well MFB-418 is located in the Bare field and produces from the reservoir MFB-53, sand U1,3; it was drilled with a horizontal length of 2000 feet (610 m) in February, 1996. The production started with the ESP system with the following conditions: 45 Hertz, 62 Amps (current consumption) and a rate of 800 bpd. The production declined to 221 bpd in two months, so it was decided to acidize the well in May 1996, obtaining a rate of 450 bpd after the stimulation. After three months it dropped off to 150 bpd, and remained with the same low production until the end of 1996.