N. Bjorndalen

Physico-Chemical Characterization of Aphron-Based Drilling Fluids

Colloidal gas aphron-based drilling fluids are designed to minimize formation damage by blocking the pores of the rock with microbubbles, which can later be removed easily when the well is open for production. Sizing colloidal gas aphron (CGA) bubbles in accordance with the rock pore size distribution is essential for effective sealing of the pores during drilling. The physical properties (i.e. viscosity, density, fluid loss, etc.) of the CGA-based drilling fluids also need to be understood in order to use these fluids more effectively. In this study, the physical properties of colloidal gas aphronbased drilling fluids are investigated. The results of rheology, API filtration loss and density measurement tests using various CGA-based drilling fluid formulations are presented. The effects of polymer and surfactant concentration, surfactant type, shear rate, mixing time and water quality on the CGA bubble size have been studied. Results of CGA bubble size characterization experiments are also reported. layer. The outer layer, which also supports the viscous layer, is hydrophobic outwards and hydrophilic inwards. Since this bubble is in contact with the bulk water, it is believed that there is another layer in which the surfactant molecules are hydrophobic inwards and hydrophilic outwards. This indicates that there is a region in between the aphron outer shell and the bulk phase layer where a hydrophobic globule will be comfortable and, therefore, oil can adhere to the gas aphron (3) . Aphrons are non-coalescing, can be recirculated, and are not affected by fine screen shale shakers. Downhole tools can be utilized with the aphronized drilling fluid system. Aphrons eliminate differential sticking by altering the near wellbore pressure drop (6) , which, in turn, reduces the need for costly downhole tools in low reservoir pressure applications (7) . One of the most important assets

Stability of Microbubble-Based Drilling Fluids Under Downhole Conditions

Colloidal gas aphrons (CGA) have the unique ability to form a bridge in the pores of reservoirs, which stops fluid invasion. Sizing microbubbles in accordance with the rock pore size distribution is imperative for effective sealing during drilling. The effects of time, temperature and pressure on the stability and size of the microbubbles needs to be better understood in order to design a fluid that will sufficiently block the pores of the formation for extended periods. In this study, the effects of time, pressure and temperature on the size of microbubbles and the stability of microbubble (CGA)based drilling fluids were investigated. The change in the CGA diameter with time was determined by using a microscopic imaging technique. Effects of base fluid viscosity and surfactant concentration on the size and stability of the microbubbles were also investigated.

Detection of Precipitation in Pipelines

Abstract One of the major unsolved complex problems confronting the petroleum and chemical industries at present is the untimely deposition of heavy organic and other solids dissolved or suspended in the fluid flow systems. The production, transportation, and processing of petroleum can be significantly affected by flocculation and deposition of such compounds in the course of industrial processing systems, including transfer conduits, reactors, and refineries and upgrading equipment, with devastating economic consequences. Heavy organics such as paraffin, wax, resin, asphaltene, diamondoid, mercaptdans, and organometallic compounds can precipitate out of the crude oil solution due to various forces causing blockage in the oil reservoir, well, pipeline, and in the oil production and processing facilities. It is important to producers that the potential organic deposition can be predicted so that the production strategy can be designed to prevent, if possible, or mitigate this problem. Cleaning the pipeline has a common commercial term, pigging. Early detection of precipitation can reduce pigging and, in turn, the maintenance cost considerably. Prediction of why and when precipitations occur has gained much interest in recent years. Most studies focus on the chemical behavior of the crude oil and its contamination. A nonintrusive instrumentation technique for on-line inspection that can yield as much detailed information about the interior of the pipe as possible is highly desirable. In this article, the detection of asphaltene and paraffin wax is studied using various techniques. The techniques include the use of solid detection system by light transmittance measurement for asphaltene detection, the use of photodiode for light transmittance measurement for liquid wax, the use of ultrasound and strain gauge for detecting solid wax.

Numerical Investigation of the Prospects of High Energy Laser in Drilling Oil and Gas Wells

Abstract Lasers are expected to provide a less expensive alternative to conventional machining and have found wide spread use in many industries. However, the physical phenomena involved in many laser applications are not fully understood. A better and more quantitative understanding of the physical mechanisms governing these phenomena will diminish the need for extensive trial and error experiments. Most of the theoretical models available in the literature have dealt with quasi-steady material removal using a continuous wave laser. This article presents a numerical model to predict the transient thermal behavior process of rocks under the influence of a pulsed laser. A wide range of parameters were considered in this study, the laser powers were varied from 0.1 to 100 kW and the lasing time was varied between 1 and 100 s. One of the results presented in this article shows that limestones consume less energy per unit volume of material removed as compared to sandstones. A comparison between the findings of this numerical study and published experimental data is also presented and shows a qualitative agreement. Finally, it is shown that numerical modeling can be useful in scaling up laboratory results to field applications.

Lasing into the Future: Potentials of Laser Drilling in the Petroleum Industry

Abstract The need for a new method of drilling oil and gas wells is immense. Current drilling techniques used were developed at the beginning of the last century. Many problems persist with this method including downtime due to dull bits, the lack of precise vertical or horizontal wells and formation fluid leakage during drilling due to the lack of a seal around the hole. Laser drilling is a new technology that has been proposed as a method to eliminate the current problems while drilling. Although experiments for laser drilling were conducted in the 1960s and 1970s, it is only recently that this research area has been redirected to the oil and gas industry. This article reviews the benefits of laser drilling, current laser types, and the experimental work that has been conducted. The experimental work conducted thus far is performed with several different lasers such as the US Armys MIRACL and the US Navys COIL. The data that was generated by these studies was executed on several types of cores including sandstone, limestone, and shale. The effect that lasing has on porosity and permeability as well as the effect of saturation and pressure on lasing was determined. The work conducted shows that a great future potential awaits the oil and gas industry with laser drilling.

Reducing Formation Damage with Microbubble-Based Drilling Fluid : Understanding the Blocking Ability

Commonly, bridging materials used to reduce formation damage and mud losses in the near wellbore region consist of solid particles. These particles need to be removed after drilling through processes such as acidizing. Microbubble-based drilling fluids utilize gas bubbles to bridge the pores instead of solid particles. These microbubbles can be removed during the initial stages of production, thereby, reducing the costs associated with stimulation processes. Although there has been some work done on the flow of microbubbles through porous media, little is known regarding what conditions (e.g. viscosity, fluid composition, pressure) determine whether the microbubbles will or will not block the pores. Both the microbubble diameter and the rock pore size distribution play roles in determining sealing of the pores. In order to gain an appreciation of the pore blocking mechanism, experiments were conducted using micro-model cells to visually understand the blocking mechanism. The composition of the fluid is varied, as well as the flow rate at which the fluid is injected. Through this, the pressure at which the microbubbles invade the medium for various compositions of the fluid for pore blocking is determined. The average microbubble size at the invasion pressure is compared to the average pore size of the porous medium. By understanding the extent of the microbubble invasion under varying conditions, a greater comprehension of the pore blocking mechanism can be established. As well, the success rate of applying the microbubble system to various types of reservoirs can be evaluated.

The Effect of Irradiation on Immiscible Fluids for Increased Oil Production With Horizontal Wells

Oil recovery using horizontal wells gives an undeniable benefit to the petroleum industry. One of the problems of using this method is that the wells can plug due to pressure and temperature changes. The components of crude oil such as asphaltene and paraffin wax can precipitate in the horizontal section of the well causing a loss of productivity and profit. Microwave or irradiation has been proposed to remove these precipitates remotely. The effect of microwaves on crude oil properties has been studied and a numerical model is presented to gain an understanding of the effect of the rise in temperature. These results include temperature increases for various concentrations of crude oil, and paraffin wax under different exposure times. The effect that different media (bentonite and gypsum) has on the temperature of these components has also been studied. By understanding the temperature rise, one can determine the effect that irradiation will have on oil production. Overall, the agreement between experimental and numerical results was acceptable.Copyright