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SPE 153468

Instrumented Yates Tail Completion: A Good Practice For MonitoringCantarell Reservoirs BehaviorJ. E. L. de Guevara, M. Gonzalez-Vazquez, R. Posadas-Mondragon, PEMEX

Copyright 2012, Society of Petroleum Engineers

This paper was prepared for presentation at the SPE Latin American and Caribbean Petroleum Engineering Conference held in Mexico City, Mexico, 1618 April 2012.

This paper was selected for presentation by an SPE program committee following review of information contained in an abstract submitted by the author(s). Contents of the paper have not beenreviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material does not necessarily reflect any position of the Society of Petroleum Engineers, itsofficers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Society of Petroleum Engineers is prohibited. Permission toreproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of SPE copyright.

AbstractAs part of the efforts to increase the productive life of wells in the Akal Field, new completion alternatives and major

workovers have been investigated. Drilling horizontal wells was considered at the beginning of 2006 in order to maximize

contact with the reservoir. The goal was to reduce the pressure drawdown at the bottom of the well and delay the water-oil

and gas-oil contact movement; however, a new issue was found: the high quantity of the almost vertical fractures that thehorizontal wells intersected in their trajectories were connected to either the aquifer and/or the gas cap. This led to consider

different types of horizontal completions that would address this issue. The completions design was equipped with blank pipe

sections intended to isolate the fractures and passive inflow control devices to force a uniform pressure drawdown along the

horizontal section. In spite of all these considerations, undesirable results were observed in some wells because in the field itwas not possible to isolate 100% of the above mentioned fractures. As a result, they ended up producing high water cuts or

high GOR.

Recently a new type of completion has been implemented in Cantarell. It is known as the Yates completion5. The application

in Cantarell consists of leaving the last 60 to 600 meters of hole section open through the Upper Cretaceous Breccia crossing

the gas cap and landing inside the oil window. The completion consists of setting up a packer/hanger with a tubing extension(tail) leaving it between 2 to 5 meters from the bottom of the borehole. The packer/hanger is anchored in the last cemented

casing string (Paleocene). The tail is made out of either open ended production tubing or slotted liner which allows the fluidsto flow from the bottom of the hole only. After several successful Yates completions, Pemex decided to install sensors in the

completion string to monitor and control the well in real time. The well selected for this application was Cantarell-3054

which was instrumented with four sensors to monitor the behavior of gas, oil, and water while the well was on production.

The results have been exciting as it is shown in this paper. These types of completions have been used all over the world,including the Middle East and the Yates Field in Texas where it takes its generic name.

The long open hole sections used in this kind of completions is benefited by the gravity drainage process, resulting in an

improved production performance; especially in formations highly fractured with high productivity indexes such as the

Upper Cretaceous Breccia. Simply stated, the Yates completion has the capacity to collect the oil being drained from theshallower gas zone and to produce it at the bottom open hole.

The implementation of this technique has been a success in the supergiant Akal field in the Cantarell Complex. From 2010 to

date, 23 completions of this kind have been implemented. Out of these, only three have underperformed. Two of these were

completed in the Lower Cretaceous horizon where the productivity and rock quality are much lower than in the Upper

Cretaceous Breccia.These type of completions also facilitates monitoring the water-oil and the gas-oil contact movement in the reservoir. The

pressure and temperature instrumention included in the Yates completion allowed monitoring of fluids contacts movement

and fluid gradient changes. From these data the bottom hole pressure drawdown is computed and the critical rate of the wellis estimated in order to avoid potential conning of water and/or gas.

This paper shows how the pressure behavior was recorded in real time during the first application of an instrumented Yates

Tail completion in Cantarell 3054. The completion was equipped with 4 sensors. Three sensors were originally in the oil zone

and one in the gas zone. At the time of writing this paper, 2 of the sensors are in the oil zone and 2 in the gas zone.