The Effect of Fracturing Fluids Types on Reservoir Fracture Geometry, Production, and Net Present Value

Unconventional reservoirs are distributed over a broad area and only generate commercial quantities of hydrocarbon using specialized technology. Tight reservoirs are reservoirs with permeability less than 0.1md. One of the leading oil fields in Iraq is Halfaya field. The tight reservoir is Saadi. It is a carbonate reservoir with poor petrophysical characteristics, moderate pores, and limited pore throats, so production from these reservoirs require hydraulic fracturing. The hydraulic fracturing can be carried out using fracturing fluid. The selection of fracturing fluids should be selected as the first step in fracturing design. The objective of this research is to find out the effect of fracturing fluids on the shape of the fracture formed. Three designs were constructed based on the fracturing fluids used to build fracturing models, where three kinds of fracturing fluids were used slickwater, guar, and hybrid (combination of slickwater and guar) with a pump rate 31.5 bpm. In the first design, the fracture's height extends up and down the Saadi formation due to the presence of fragile layers around Saadi formation, so fluids are produced from these three formations. In the second design, the fracture's height is limited within the Saadi formation from the top but extends to the Tanuma from below, and therefore the production will be from the Saadi and Tanuma reservoirs. Three hybrid treatments were analysed: 30% guar & 70% slickwater, 50% guar & 50% slickwater, and 70% guar & 30% slickwater. The results show that the third design (50% guar & 50% slickwater) give the best oil production and NPV

CALCULATION OF VOLUMETERIC AND THERMODYNAMIC PROPERTIES FOR PURE HYDROCARBONS AND THEIR MIXTURES USING CUBIC EQUATIONS OF STATE

The objective of this study was to develop a complete package for prediction of volumetric and thermodynamic properties of pure hydrocarbons fluids and their mixtures in one and two phase regions. Two cubic equations of state that are Peng-Robinson and Soave-Redlich-Kwong were used with volatile and black oils respectively to calculate the desired properties in addition to bubble point and dew point pressures and temperatures. Different values of binary interaction parameter were used for each equation and effects of this parameter values on the prediction are examined. Also values of this parameter between the plus-fraction and other component have been evaluated for first time. In calculation of heat capacity, four different mixing rules have been proposed to evaluate the temperature derivatives in case of the mixtures. Wide comparisons with the literature experimental data were made which indicated that both equations of state predict accurately different properties and marked improvements are achieved by use binary interaction parameter other than zero. Also both equations predict bubble point pressure of a certain mixture approximately with same accuracies using the recommended values of binary interaction parameter. Among the proposed mixing rules, Kay’s one appeared the best one to determine temperature derivatives

STRATIFIED WATER-OIL-GAS FLOW THROUGH HORIZONTAL PIPES

Stratified three-phase flow through horizontal pipe has been studied experimentally. The fluids used in the system are water, kerosene, and air. A closed loop flow system, which composed of 0.051 m inside diameter and 4 m length test pipe, is designed with facilities for measuring flow rate, pressure drop and thickness of each phase. The effects of gas, liquid flow rates and water liquid ratio (WLR) have been experimentally observed. It was found that liquid (water, and oil) thickness decreased when the gas flow rate is increased with constant liquid flow rate, and increased when the liquid flow rate is increased at constant gas flow rate. Pressure drop increased when the gas and/or liquid flow rate is increased. Three equations have been formulated, using the experimental data of the present work, to predict liquid, water thickness and system pressure drop in stratified three-phase flow in horizontal pipe. High correlation coefficients are obtained for these equations. The experimental results are compared with the results obtained from three-phase model of Taital, Barnea, & Brill (1995). The comparison showed that the predicted data which obtained from three-phase flow model Taital et al. (1995) is in good agreement with experimental data

APPLICATION OF MATHEMATICAL DRILLING MODEL ON SOUTHERN IRAQI OIL FIELDS

Minimum-cost well drilling demands the best use of controllable drilling variables for each formation to be drilled. To reach this aim, this study was divided into two main parts: The first part deals with applying a mathematical drilling model to field data of forty wells drilled at three major oil fields (RU, R, and Z). Bourgoyne & Young (1974) drilling model has been modified to take into consideration the combined effect of weight on bit, rotary speed, bit type, bit size, flow rate, drilling fluid density, drilling fluid viscosity, oil content, bit-nozzle size, formation drillability, formation abrasiveness, bit bearing constant, formation hardness, formation compressive strength, differential pressure between mud column pressure and formation pressure, and bit dullness on drilling rate at these fields. The measurements of formation compressive strength have been achieved using 34 core plugs. These plugs were cut and prepared for soft, medium, and hard formations under study. The drilling model was fitted to Field data by using multiple regression analysis technique. The results of analysis gave low standard deviation, high correlation coefficient, and good matching between measured and calculated drilling rate. The validity of modeling process has been verified by applying the proposed drilling model on other wells that have not been included in the main analysis. The second part deals with using the drilling model together with non-linear optimization technique to determine the optimum values of the controllable drilling variables. These variables are: weight on bit, rotary speed, flow rate, drilling fluid density, drilling fluid viscosity, oil content, bit-nozzle size. Using the proposed mathematical drilling model together with the Constrained Rosenbrock optimization technique achieved a marked reduction in drilling cost about 60%, 75%, 80% in soft, medium, and hard formations respectively. The results of optimization were used to construct optimum bit record for the next wells to be drilled. For comparison purpose, this optimum bit record has been used to reduce the drilling cost for well RU263 and saved about 295000 $in the total cost of this well which is equal to 394176$