Improved Oil Recovery by Cyclic Injection and Production

Abstract

Cyclic waterflooding is an IOR-method that improves oil production in heterogeneous reservoirs with high-permeability contrast. The concept of the method is based on pulsed injection and alternating of waterflood patterns. The main effect induced by the cycling of wells is oil production increase accompanied by water production decrease. The production increase is achieved by improved sweep efficiency in low permeable zones of a reservoir non swept by traditional waterflooding process. The cyclic water injection process was successfully applied in a number of sandstone and carbonate oil fields in Russia, USA and China. The important advantages of the method are virtually zero additional cost and simple implementation procedure. The uncertainty with the method is related to understanding the IOR mechanism, ability to accurately model the process and design a field application. The paper presents the results of the study of cyclic water injection and oil production at a North Sea heterogeneous sandstone reservoir. The study consists of the field history analysis, pre-screening cyclic efficiency estimation and numerical reservoir simulation to design the field application of the IOR-method. The field history analysis shows the presence of cycles in injection and production and their influence on water-cut change. Pre-screening analytical tool was used to perform a wide-range sensitivity analysis with respect to rock-fluid parameters, heterogeneity, cycle length and pressure conditions in order to understand the mechanism and to estimate the IOR potential. Finally the sector model reservoir simulation was used to optimize the cyclic process by alternating the waterflood patterns and to design the field application. The simulations show decrease of water production and improvement of oil production by up to 3% with short time and by 5% with long time cycles. Introduction The cyclic waterflooding improves sweep efficiency in heterogeneous reservoirs. In the IOR-method a combination of two processes of (1) pulsed injection (production) and (2) alternating of waterflood patterns is used. The cyclic waterflooding was successfully applied in a number of sandstone and carbonate oil fields in USA1,2 and Former Soviet Union 3,4,5. The cyclic injection potential was evaluated in a number of studies 3,4,5,6,7,8. Analytical estimation and numerical simulations have shown significant potential with oil production increase by up to 10% and reduction of water-cut by up to 20%. Recent experimental studies 9 have demonstrated improvement of oil recovery under pulsed pressure conditions at laboratory scale. The uncertainty of cyclic waterflooding is related to understanding of the IOR mechanism, ability to model and predict efficiency of the process, and to design a field application for specific reservoir conditions. In this paper we analyze production and injection data, discuss and evaluate parameters that affect cyclic waterflooding, estimate efficiency of the method for different scenarios of field application. Cycling effects which occurred in the production history of a heterogeneous sandstone reservoir were analyzed to evaluate their influence on water-cut behavior. The analytical tool 8,10 was used for screening of the cyclic injection. A wide range sensitivity analysis was performed to estimate efficiency of the cyclic process. Based on the analytical screening results the numerical simulations of cyclic waterflooding were carried out on a sector reservoir model. IOR potential of cyclic reallocation of water injection volumes between well patterns was also estimated.

A comparative experimental study of IOR potential in fractured shale reservoirs by cyclic water and nitrogen gas injection

“…The recovery performance of cyclic water flooding in conventional reservoirs has been demonstrated by lots of experimental and simulation studies as well as field practice reports (Li et al, 1995;Stirpe et al, 2004;Shchipanov et al, 2008;Surguchev et al, 2008). The concept of such cyclic injection is based on (1) pulsed injection and (2) alternating waterflood patterns.…”

A Tracer Streamline Practice for Re-Evaluation Waterflood Pattern to Introduce a Cyclic Water Injection Scheme

“…Since then, the cyclic water injection has several times applied in some fields in the world, in China, the United States, and Russia. Those have shown positive results (Shchipanov et al, 2008) CWI has a result that is not as good as other EOR methods. Because of a less incremental recovery when compared with other EOR methods, the CWI is considered an advanced waterflood (Rublev et al, 2012).…”

“…Oppositely, whereas low injection rate into the reservoir cause pressure drops significantly. Once cyclic injection takes place, there should be a pressure pulse between the layers (Shchipanov et al, 2008) As for some of the advantages of the application of cyclic water injection, including: 1. Increase oil production (Perez et al, 2014) 2.…”

Experimental Study on Dynamic Characteristics of Shut-In and Restart Process in Water Drive Strong Heterogeneous Oil Reservoir

“…It means that it not only generates additional pressure drop at the injection well region but also generates additional pressure drop at the production well region. The additional pressure drop between the higher and lower permeability layers causes the oil and water exchange and seeps into the seepage channels [29]. Thus, with the activation of the dead oil region by periodic variations of the additional pressure field, the capillary force effect and elastic effect are fully used.…”