A Comparison of Dry Forward Combustion With Diverse Well Configurations In a 3D Physical Model Using Medium And Low Gravity Crudes
Authors: Bagci S. , Shamsul A. 
Published: March 2010

A comparative laboratory analysis of dry forward combustion was accomplished with the application of different well configurations in a 3D semi scaled model using medium and low gravity crudes. The model represents one-fourth of a five-spot pattern in Raman and B. Kozluca fields, both of which are located in Turkey. The model was scaled to be most representative of Raman field whilst, it merely corresponds to a geometrically similar prototype in B. Kozluca field.

Seven experiments using Raman crude (18.3 ° API) and four experiments using B. Kozluca (12.4 ° API), were carried out in the laboratory with a 40 cm square 3D model having a thickness of 15 cm. Five different well configurations were applied to recover Raman crude while four different well configurations were studied with B. Kozluca crude. The model was packed by tamping a mixture of crushed limestone, water and crude oil. A total of 36 thermocouples were used at the top, centre and bottom planes to measure 3D temperature distribution and to track the trailing front during the experiments. An ignitor was placed near the vertical injector. Air was injected through this vertical injector in each experiment following a period of pre-heating. To determine their effects on oil recovery and process variables, all of the well configurations were studied using both crudes except dual horizontal producers, which was only used with Raman crude.

The highest oil recoveries for both crude oils were obtained with horizontal producers positioned at the boundary of the model alone as a single producer. With a same burned volume more oil was recovered by horizontal producers than by vertical producers. In all the cases recovery decreased with a decrease in API gravity as would be expected. Air requirement and fuel consumption were reduced greatly by applying horizontal producer. But for a certain well configuration air requirement and fuel consumption were higher with lower gravity (12.4 ° API) crude. The process variables such as front velocity, fuel consumption rate, injection and production pressures and sweep efficiencies were investigated for both the crudes to assess process performance.

Introduction

Over the past 40 years, dry forward combustion has received a great deal of attention. The process involves ignition of formation near the injection well, followed by the propagation of combustion front through the reservoir. Combustion front is sustained by the injection of air into the formation through one or more wells. The vapourization and condensation of oil and formation water take place simultaneously near the combustion front and in the cooler part of the formation during the propagation of the front. The condensed fluids, in turn, push oil into the producing well bores.

Until recently, most of the thermal recovery processes have been implemented by employing vertical wells but the present-day drilling technology facilities the application of horizontal wells in thermal recovery processes. Horizontal wells have numerous advantages. They provide a larger areal contact and, hence, higher recovery than conventional vertical wells. This is especially true for thin reservoirs where in vertical penetration is uneconomical.