Innovative Water-Shutoff Solution Enhances Oil Recovery From a West Venezuela Sandstone Reservoir

Abstract

With the discovery of new fields becoming less common and the continued development of brownfields, water control is becoming increasingly essential to enhancing oil recovery. Water control operations are especially challenging in under-pressured reservoirs with openhole completions, such as in the Boscan field in West Venezuela. Gravel-packed slotted liners and standalone premium screens are common completion methods in this field. Dual injection, combined with permanent water shutoff (WSO) gels or relative permeability modifiers to control water production in these completions has traditionally produced inconsistent results. This method can fail to change the well production profile and possibly damage oil-producing layers. This paper will discuss the development, implementation, and results of an innovative solution for water shutoff that was engineered for the complex completion methods mentioned. The solution involves three key stages; the temporary isolation of the producing layers, the permanent shutoff of the water zones, and the effective cleanup of the isolated producing layers. The results of ten water control treatments are presented here. The average water cut was reduced to 30% from 88% and oil production was increased by an average of 300 BOPD per well through the application of this water shut-off solution. In one particular well, two previous water control treatments using a conventional water shutoff technique, including a relative permeability modifier (RPM), had left the well producing 100% water. The new solution reduced the water cut to 25%, resulting in a gain in oil production of 300 BOPD. This innovative solution was established as a standard practice for water shutoff in the Boscan field. Introduction The Boscan field lies 40-km southwest of Maracaibo, Venezuela and covers an area of approximately 660 km2, produces a 10.5°API gravity asphaltic oil from the upper Eocene, Boscan (Misoa) Formation with a live oil viscosity ranging from 200–400 cp at reservoir conditions. The reservoir dips to the southwest and ranges from 5000 to 9000 ft in depth. Boscan Field is a combination structural/stratigraphic trap. The reservoir sands were deposited in a tidal-dominated depositional setting. Boscan Field has a complex stratigraphic framework, the interpretation of which is made particularly difficult by the 1 to 0.6 kilometer well spacing. The field currently produces ~ 115,000 BOPD. Figure 1 shows the geographic location of the Boscan field. Since its discovery by the Richmond Exploration Company in 1947, the Boscan field has had over 800 wells drilled with 525 of them currently active. Most of the shut-in wells in the field are located in the south end of the field that in recent years has experienced a surge in water production. Most of the wells in this particular area are experiencing water cut of 90% or higher. Problem Scope The main production challenges in south Boscan wells are;Surface facility limitations in handling produced water; therefore the volume of fluid produced is limited. In addition, production enhancement is restricted.