Abstract

A water management strategy was initiated in the North Uthmaniyah area of Ghawar field in late 1999. The strategy main objectives are to reduce operating expenses associated with water handling and avoid capital investment required for the expansion of water handling facilities while engendering a more efficient recovery process. The strategy was implemented through four initiatives: operating of high water cut wells on a cyclic basis, conducting rigless water shut-off jobs, drilling horizontal sidetracks of existing vertical completions and drilling wells with partial penetration completions. All of these practices were designed to leverage Ghawar Arab-D advantages of high reservoir conformance and displacement efficiency, which will ultimately yield high oil production with minimal water production.

The techniques of operating of high water cut wells on a cyclic basis and rigless water shut-off jobs have been successful in slowing down water production at low cost. Based on the recent encouraging results, it appears economically and technologically feasible to produce the remaining oil at lower water production rates, by drilling horizontal sidetracks during the middle and later production periods in mature fields concurrent with a rigorous surveillance and monitoring program. Finally, wells with partial penetration completions have been introduced to the area recently to delay water production and accelerate oil production.

Introduction

North Uthmaniyah represents one of the most mature areas in Ghawar field, the largest field in the world. It was discovered in 1948 and placed on production in the early 1950’s. It produces Arabian light oil with average API gravity of 32.6° and GOR of 550 SCF/STB. Matrix porosity and permeability averaged 18% and 220 MD respectively.

The field is under peripheral injection water flood. Water injection distribution on the periphery varies with withdrawals. Water sources are primarily seawater from the Arabian Gulf, and re-injected produced water. Produced water and sea water are injected through separate systems.[1]

Fig. 1 shows the historical water cut performance in North Uthmaniyah. Although the field has maintained the capability of producing at high oil rate, water production has been successfully reduced and kept water cut stabilized at almost 46% over the past five years after implementing water management.

Excessive water production can lead to a loss in production potential. It also leads to increase production cost with higher field capital investment requirements in surface facilities to handle produced water.

In late 1999, an active water management strategy was initiated to minimize water production while maximizing oil production at lowest cost. This strategy was implemented through the following four field practices:

1. Cyclic production modes.

2. Rigless water shut-off (WSO) jobs.

3. Horizontal drilling sidetracks.

4. Partial penetrated wells.

The purpose of this paper is to highlight on this successful water management strategy in North Uthmaniyah.

Water Management Practices

As the water flood matures, water breakthrough occurs in the lower zones of the oil wells and production rates decline due to increased flowing pressure gradients.[2] Water management is an important aspect of our overall management strategy, especially in a relatively mature area like North Uthmaniyah.

The excessive water production constrains production facilities needed to handle it, but, more importantly, can hamper sweep efficiency. Reducing water production will also maximize oil production from top zones. The above mentioned practices of water management will be discussed in detail in the following sections.