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Leak-off Tests (LOT) and Pressure Integrity Tests (PIT), are verification methods to evaluate cement jobs and estimate the formation fracture pressure at the casing shoe. Although analysis of LOT in deep wells is considered a well known and practical procedure, the interpretation of LOT in Shallow Marine Sediments (SMS) is less clear. LOT in SMS gives a non-linear relationship between the pumped volume and the observed pump pressure and there is no obvious point of deflection or "leak off" from the initial linear section of the plot. Because of non-linearity of LOT plots in SMS, LOT could be inconclusive and difficult to interpret. Incorrect interpretation of LOT would lead to costly problems that might jeopardize well progress such as; unnecessary squeeze jobs, premature setting of casing, and lost circulation problems. This paper presents a new method to analyze casing shoe leak-off pressure in the SMS. A mathematical model is derived to assist in analyzing non-linear LOT behavior and the new method is supported by field data from LOT in SMS. LOT interpretation is the basis for the critical drilling decisions such as; casing setting depths, cement job evaluation, drilling fluid selections, and well control methods. Correct interpretation of the LOT can help to avoid variety of problems and save considerable amount of time and money. Introduction Shallow water flow, gas migration, cratering, and underground blowouts can be prevented only through appropriate casing design and cementing jobs. The LOT is relatively simple field procedure to determine fracture gradient. Since, the LOT is a measure of the strength of the formation or the integrity of the cement at the casing shoe. Leak-off pressure determined from the test is a measure of the maximum pressure that may be imposed at the casing shoe. Although the LOT is a simple almost mechanical procedure, the outcome of the test can be hard to interpret, particularly in formations that give nonlinear relationships between the pumped volume and the observed pump pressure. Generally, in shallow marine sediments LOT procedures are conceptually the same as for the deep sediments. The difference is that in deeper sediments the beginning of formation failure is easy to recognize, which is not the case for the shallow and soft rocks.

Although the use of compressible drilling fluids is experiencing growth, the flow behavior and stability properties of drilling foams are more complicated than those of conventional fluids. In contrast with conventional mud, the physical properties of foam change along the wellbore. Foam physical and thermal properties are strongly affected by pressure and temperature. Many problems associated with field applications still exist, and a precise characterization of the rheological properties of these complex systems needs to be performed. The accurate determination of the foam properties in circulating wells helps to achieve better estimation of foam rheology and pressure. A computer code is developed to process the data and closely simulate the pressure during drilling a well. The model also offers a detailed discussion of many aspects of foam drilling operations and enables the user to generate many comparative graphs and tables. The effects of some important parameters such as: back-pressure, rate of penetration, cuttings concentration, cuttings size, and formation water influx on pressure, injection rate, and velocity are presented in tabular form. A discretized heat transfer model is formulated with an energy balance on a control volume in the flowing fluid. The finite difference model (FDM) is used to write the governing heat transfer equations in discretized form. A detailed discussion on the determination of heat transfer coefficients and the solution approach is presented. Introduction Stable foam could be described as a special type of aerated drilling fluids. Foam is made up of a mixture of incompressible fluids injected with compressed air or other gases. In foam as a gas-liquid dispersion the incompressible fluid is the continuous phase and the gas is the discontinuous phase. The incompressible component is usually the mixture of treated fresh water and a surfactant foaming agent. Additives and foaming agents such as polymers, graphite, and asphalt can be added to the foam as viscosifiers, stabilizers, lubricants, and corrosion inhibitors. The compressible component is usually air, nitrogen, natural gases, and rarely CO2.

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