Research And Field Application Of Water Coning Control With Production Balanced Method In Bottom-Water Reservoir
Authors: Tu Xingwan , Peng Dragon L. , Chen Zhaohui 
Published: December 2007

Water coning is the most threaten to the oil production in the bottom water reservoir. The formation water will go far faster than oil, as a result, some oil wells with massive productivity could be killed by the high water cut and the utilization of natural driving force is reduced to an unacceptable level. A balanced production adjusting method which based on the well controled reserves is presented in this paper. This method is combined with the uneven factor of utilization to natural energy, the uneven factor of oil recovery rate and the uneven factor of drawdown rate. It will be used to guide the production control through the drawdown, oil recovery rate and reservoir energy depletion to make the recovery balanced and the WOC balanced. It is applicable and reasonable proved by the field reservoir simulation and the WOC can be balanced and the production can be enhanced.

Introduction

Active bottom water is a kind of natural driving force which can improve the development effect if reasonable production control is implemented. Otherwise, water channeling and coning will occur and lead to a significant decrease in well productivity.

Water channeling in bottom water reservoirs is one of the main reasons that cause a rapid drop in production rate during the mid-later development stage. For the high production wells with good physical properties, if no dynamic adjustment in oil rate is made, unreasonable oil production allocation will result in large water production and even wells killed during the later stage. Stabilizing oil production and controlling water production becomes the most important issue during the development of bottom water reservoirs. In the aspect of the current production techniques, the main methods to water control include selective water plugging, chemical gelled baffles, optimized perforation, horizontal wells, artificial baffles near the oil-water contacts, etc. In the aspect of reservoir engineering, the main methods are to monitor the dynamic oil-water contacts through the observation wells, and to calculate the critical oil production rate before water coning using theoretical models, and to predict the no-water production period and oil-water production period. However, it is difficult to tell by observation wells the exact oil-water contacts which move up inconsistently, and therefore water breakthrough in some wells happens earlier than predicted while too low production rate is allocated unnecessarily in some other wells, which causes production loss and development benefit decreasing.

The methods to balance well production allocation are researched in this paper through reservoir energy, well controlled reserves, reservoir connectivity and fluids flow characteristics. A parameters system to evaluate the balanced production is built using the concept of uniformity coefficient in statistics, and three unevenness factors, which are unevenness factor of natural energy utilization, unevenness factor of oil recovery rate and unevenness factor of drawdown rate, are defined. The purpose of the balancing production is to keep the oil production in stable and control the bottom water production.

This evaluation method is applied in a bottom water reservoir. A production allocation adjustment plan is made, and the reservoir numerical simulation is used to predict the dynamic performance of this reservoir. The result demonstrates the applicability and reasonableness of this method.