One of the concerns of hydrocarbon resource companies is how effectively their wells have been cemented. One of the methods of evaluating cement quality has been with cement bond logs. Conventional cement bond logs have not always been conclusive, even in supposedly excellent cement, or alternatively in supposedly "free--pipe" situations. A decision to attempt a remedial cement repair in an indicated poor cement situation may not be successful. A decision not to attempt a remedial cement repair in an indicated good cement situation may result in unwanted fluid production from an adjacent zone.
This paper will present examples and discuss the effects of high gel cements, pipe eccentralization and Channeling on current cement quality tools. A discussion leading to a suggested interpretation of current cement quality log results with respect to repairability of the cement will be presented. During the discussion of the interpretation method, several examples will be presented showing possible predictability of determining what will yield first during a cement squeeze, the cement or the formation.
Limitations of the interpretation methods will be presented and discussed.
Suggestions for future studies and improvements will be outlined.
The efficiency of a tertiary oil recovery process will be affected when the injected fluid(s) react chemically with the reservoir rock.l Chemical reaction between the rock and the injected fluid could be in form of fluid adsorption on to the rock surfaces or rock dissolution by the injected fluid. In microemulsion flooding, the efficiency of the process is affected by surfactant adsorption on to the rock surface.1 Holm2 reported a study in which the permeability of a dolomite core increased threefold after about nine pore volumes of carbon dioxid.e slug and carbonated water was injected through the core. This is a case of rock dissolution by the injected fluid. CrawEord et. al 3 reported a case history in which the use of carbonated water as postfracture treating fluid resulted in rapid and complete well cleanup.
Formation of stalactite and stalagmite in caverns show that. although carbon dioxide does dissolve carbonate rocks in the presence of water, the reaction is to some extent reversible in nature. This understanding can be extended to the reaction between CO2 and the rock in CO2 flooding of carbonate reservoirs. Since many carbonate reservoirs (mostly dolomite are potential candidates for CO2 flooding, there is a need, EOR an in-depth study of the reaction between CO2 and dolomite rock. The object of this study was to investigate the effect of CO2 on dolomite rocks and the effect of pressure on CO2-dolomite rock interaction.
The purpose of this paper is to present the result of the investigation to show that while CO2 can dissolve pore linings of carbonate rocks and increase the rock permeability near the injection well, calcite crystals are precipitated and are deposited in the flow path when the pressure is reduced.