Research is Good, But Does It Help?
Authors: Yeung F.B. 
Published: March 2010

Introduction

The continuous search for energy routinely forces us in North America to analyse reservoirs classified as more challenging than those in other parts of the world. The problems associated with these reservoirs can sometimes lead to a fairly complex optimization problem. This is the point at which the approach taken by various engineers and companies may deviate. The best engineers are those who can guess the approach to be taken and, due to their intuition, have great success. There is no substitute for prophecy. Unfortunately, the majority of us are faced with the necessity of trying to describe the optimal exploitation strategy by comparison to experimental and/or theoretical devices which tend to identify key parameters and improve our forecasting capability.

With this in mind, it is obvious that much of scientific and engineering research has been applied to improve our ability to resolve the challenges of deeper, hotter, solids-containing and tighter reservoirs, but how much has this science really helped us?

I would like to take three separate areas of petroleum engineering and address improvements which have occurred in the last few years and the impact that these technologies have had on the costeffective production of hydrocarbons from difficult reservoirs.

Organic Solids Precipitation

Much research and development has been perfomed in this area, particularly over the last 10 years. Many experimental techniques and theoretical models have been developed for assessing such things as incipient precipitation conditions, solid phase envelope determination, influence of chemical additives and techniques for remediating solids precipitation problems in the wellbore, such as coated tubing. The work conducted by many authors(1–8) notwithstanding, questions still abound as to what is the best way to minimize the expense associated with solids precipitation.

For paraffinic systems, a test commonly performed is cloud point determination. For the type of system analysed in Figure I, where a cloud point for a specific fluid is observed, this is important information to have. Nevertheless, giving this to an operating engineer may be of little use. This information, however, can be used in conjunction with available wellbore models to produce the type of scenario shown in Figure 2, where one can identify the depth at which solid precipitation is going to occur.

This technology has been applied within the last 18 months and new wells which have been drilled in this formation are being completed with a down to the depth indicated by a combination of the experimental results and the theoretical models. In this case, the benefit of being able to identify the pressurized cloud points and where the cloud point constraint was going to be violated was essential information to have when designing the wellbore.

For asphaltene-dominated precipitation aromatic solvents (xylene toluene) have been routinely used to solubilize the solids once precipitated. There have been improvements in chemical technology whereby the use of high molecular weight additives appears to stabilize solids in the oil, thus changing the mechanism by which solids precipitation occurs.