Integrated Perspective Assessment For Complex Low-Permeability Reservoir
Authors: Selemenev S. , Vasiliev Andrey , Kolesova M. , Shekian Arthur 
Published: October 2008

The recent advent and commercialization of new fracturing and horizontal drilling technologies aroused interest for potential development of complex low-permeability reservoirs. For these type of reservoirs can be classified Achimov and Jurassic formation of West Siberian basin with low reservoir quality (permeability less than 1 mD and porosity values less than 0.15). Current estimations taken in recent years bespeak that the volumes of these resources are quite huge, but its development is in demand of principally new approaches. The development of such resources will require new technologies and methods in the whole work process - from analytics and 3D modeling to well completion and stimulation. Evaluating the possibilities of perspective assessment of one of the oil fields located in Nadym depression it had been taken an attempt to find optimal way of completion, well planning, taking into account geology of the field. This study we based on the modern methods of 3D geologic and simulation modeling, which play principal role in choosing the development plan and in drilling also.

Introduction

The rising interest to the hard to recover reserves can be discussed from the point of "Pyramid of resources" conception worked out by American scientists [1]. This conception is based on hypothesys that mineral resources are distributed log-normally. This distribution of mineral resources such as gold, uranium, silver and others is described in literature. The high-quality reserves of these minerals are quite rare and small. Resources of considerably low quality occur much often but the development is usually not rental. The main factors which can transfer reserves from non-rental to rental are the increase of price on the product and developmrnt of technologies that can decrease the final cost. This approach can be taken also for the hydrocarbon reserves.

On Fig.1 it can be seen that the volume of reserves of high quality in homogenius reservoirs with high permeability is quite small if we compare it with the volumes of low-quality reserves. In old oil provinces which have long history of development the reserves of the top of pyramid are explored and probably taken. The reserves of low quality in these provinces are explored but development was not started because of low reservoir quality and low initial rates. For decades these reserves sere not developed. The best examples are "ryabchik" reservoir of Samotlor field and Priobskoye field.

In last 20–30 years the technologies of oil and gas recovery had significant progress. Especially it is related to the methods of reseiervor investigation, horizontal drilling, production optimization. A great step forward was taken by computer methods of modeling of the fields. All these methods allow to make more exact prognoses of reseirvor properties and to have more exact production plans. This creates an opportunity to continue development of reserves in the basement of the pyramid. The volumes of such quality may be considerable. The estimates done by SibNAC geologists show that summary recoverable C3+D0 reserves of hydrocarbons of Achimov and Jurassic firmations only in Yamal-Nenetsky region are nearly 13.6 billion tons of oil equivalent [2]. To prove these resources and to start development there is a need to find principally new approaches for production optimization. Evaluating the possibilities of development of one of the fields of Nadym region, we made an attempt to make integration of available for today technologies in geologic and hydrodynamic modeling, drilling and well completion to find the optimal case.