Variations of hydrostatic pressure over the sea floor, are transmitted through the lithological layers by stress waves. These waves induce changes in the pore pressure, when reaching the subterranean reservoirs. This work models the oceanic tidal effect on a infinite reservoir by coupling geomechanic principles with equations for fluid flow in a deformable porous media. The problem is treated in the context of test analysis, concerning dimensionless form of variables and the inclusion of well effects. The results are incorporated to conventional type curves, and were validated by comparison with real and simulated pressure test data. Alternate practices were suggested to integrate the well test analysis in reservoirs affected by the tidal effect. Introduction Tide is a result of the relative displacement of the particles composing a celestial body, caused by gravitational attraction of neighboring bodies. On Earth, comprehended by a gas cap, a water mass and a rock volume, the relative movement of these phases is the base of the known barometric, earth and ocean tides. At a reservoir located under the sea floor, the three tidal mechanisms are active over the rock-fluid system. The ocean tide is, however, by the magnitude of its effects on the reservoir, the dominant source of perturbation. The propagation of the pressure perturbations from the ocean floor to the reservoir is not conservative, and the ratio between the pressure variation at these two locations is known as the tidal efficiency. Though the first observations of the phenomenon are dated of the end of last century, the phenomenon had not been detected in the oil industry until the advent of highly sensitive pressure recorders, about two decades ago. In 1976 Kuruana presented the first work relating the periodical pressure oscillation during testing of wells in Timor sea with the ocean tides. Hemala and Benalves in 1986 provided an overview of tidal effects from petroleum engineering point of view and proposed some possible applications of the effect to predict fluid heterogeneities in reservoir. Inspired on the Hemala's proposal, Wanell and Morrison presented a practical method of measuring vertical permeability and Dean et al introduced a method to monitor compaction and compressibility changes in offshore chalk reservoir by measuring the tidal effect in the reservoir. In well test analysis the tidal effect appears as unwelcome perturbations troubling the diagnostic mainly at the late time periods. So far, little has been done to incorporate the theoretical modeling of these effects to the conventional practice of formation evaluation. In the present work, the tidal effect is addressed according to he interest of well test analysis. The focus is on a infinite reservoir model producing at a single well and being simultaneously affected by the variations in the overburden pressure caused by the ocean tide. A fundamental study on this topic necessarily involves the basic concepts of geomechanics, the principles governing the tidal phenomena and the theory of fluid flow compressible porous media. The objective of the present paper is to present a model coupling aspects of these three distinct areas, including a theoretical solution given in the form commonly used in well test analysis and finally propose some procedures to help in the diagnostic of pressure records that are affected by tidal waves. Theoretical Background To address the problem properly, it is important to begin by stressing on the concept of rock compressibility. Such concept is used both in geomechanics and fluid flow in a nonuniform, and very often mistaken, terminology. P. 301^

fax 01-972-952-9435. AbstractThe Campos Basin mature fields, offshore Brazil, including the Marlim Field, are usually referred to as the World's deepwater field laboratory. The development of these fields was driven by the Brazilian state energy needs throughout the seventies and eighties, which induced a strategy of accelerating the projects implementation and anticipating their first oil. This sense of urgency is still dominant in Brazilian oil politics and has recently enabled the country to reach its oil self-sufficiency. That scenario throughout the last two decades encouraged risk assumption as well as the implementation of a considerable number of new technologies. Fifteen years after the first oil production from Marlim it seems that more engineered solutions are replacing the daring initiatives and the concise studies carried out in the beginning. Those years also testified an outstanding evolution of the drilling and completion technologies. The development advance to deeper and deeper waters brought up unpredicted problems such as wax deposition and hydrate formation. Thus, the history of the mature deepwater fields of Campos Basin offers great opportunities for learning, in a wide perspective. This paper summarizes the history of the damage and main completion troubles associated to Campos Basin deepwater mature fields. The aspects of prediction, prevention and remediation of the formation damage associated to drilling, sand control, stimulation, fines migration, organic deposition, scale, souring and other minor issues are addressed. The paper also presents some statistical data, predicted and unpredicted problems, and the ways they have and are currently handled. The technologies evolution and the most recent challenges are also shown. It is our belief that other deepwater mature fields to be developed and the new systems to be designed will certainly benefit from the experiences and lessons learned in the deepwater mature fields of Campos Basin. SPE 106389porosities, requiring the installation of sand exclusion systems, either in the producers or injectors wells. The development of the deep and ultra-deep fields has been accomplished by using floating platforms and subsea completions, associated to complex subsea layouts. The wells evolved from vertical and deviated to complex horizontal and extended reach, high rate ones. In this scenario damage is usually very expensive to be removed and implies large production loss.This paper provides a summary of the CB context evolution throughout the years with respect to: national energy politics, technological challenges, human resources, organizations structures, and the history of offshore installations. It also presents a section on damage identification methodology and its history considering the type of damage, and finally a few conclusions.

Modern logging tools, including Nuclear Magnetic Resonance (NMR), allow geoscientists to integrate data and use advanced petrophysics techniques. The NMR logs estimate permeability curves based on empirical equations and their response are sensitive to the permeability trends in rock layers of a heterogeneous reservoir. Therefore, it is possible to define flow units based on NMR flow capacity. This process can even be enhanced if there are Production Logging results available. This paper presents a technique applicable to well test interpretation which consists in estimating the permeability of flow units through the integration of NMR, formation tests and production log data. The properties of each flow unit such as thickness, average permeability and effective porosity are estimated from the NMR log. Using these data a multilayer flow model is built, in order to determine a multiplicative factor for the prior defined average permeability from each flow unit honoring the results of DST data. Several simulations are performed by changing the horizontal and vertical permeabilities and skin factor for each flow unit, to obtain compatible results with the well test. This technique is applied in Brazilian carbonates. The cumulative NMR permeability curves shows good agreement with PLT data, which means that the NMR can be used as a predictive flow unit identifier when PLT data are not available. In conclusion, the technique permits the interpreter to test various scenarios in a multilayer model, using different combinations of permeability and skin values for the flow units. This petrophysical model can also be used as an input for the dynamic simulation of the reservoir.

fax 01-972-952-9435. AbstractThe Campos Basin mature fields, offshore Brazil, including the Marlim Field, are usually referred to as the World's deepwater field laboratory. The development of these fields was driven by the Brazilian state energy needs throughout the seventies and eighties, which induced a strategy of accelerating the projects implementation and anticipating their first oil. This sense of urgency is still dominant in Brazilian oil politics and has recently enabled the country to reach its oil self-sufficiency. That scenario throughout the last two decades encouraged risk assumption as well as the implementation of a considerable number of new technologies. Fifteen years after the first oil production from Marlim it seems that more engineered solutions are replacing the daring initiatives and the concise studies carried out in the beginning. Those years also testified an outstanding evolution of the drilling and completion technologies. The development advance to deeper and deeper waters brought up unpredicted problems such as wax deposition and hydrate formation. Thus, the history of the mature deepwater fields of Campos Basin offers great opportunities for learning, in a wide perspective. This paper summarizes the history of the damage and main completion troubles associated to Campos Basin deepwater mature fields. The aspects of prediction, prevention and remediation of the formation damage associated to drilling, sand control, stimulation, fines migration, organic deposition, scale, souring and other minor issues are addressed. The paper also presents some statistical data, predicted and unpredicted problems, and the ways they have and are currently handled. The technologies evolution and the most recent challenges are also shown. It is our belief that other deepwater mature fields to be developed and the new systems to be designed will certainly benefit from the experiences and lessons learned in the deepwater mature fields of Campos Basin. SPE 106389porosities, requiring the installation of sand exclusion systems, either in the producers or injectors wells. The development of the deep and ultra-deep fields has been accomplished by using floating platforms and subsea completions, associated to complex subsea layouts. The wells evolved from vertical and deviated to complex horizontal and extended reach, high rate ones. In this scenario damage is usually very expensive to be removed and implies large production loss.This paper provides a summary of the CB context evolution throughout the years with respect to: national energy politics, technological challenges, human resources, organizations structures, and the history of offshore installations. It also presents a section on damage identification methodology and its history considering the type of damage, and finally a few conclusions.

To address the uncertainty in both the monitoring and the forecasting of the environmental conditions for offshore operations, DNV recommends the use of Alpha factors. These factors are defined for the environmental conditions in North Sea and the Norwegian Seas. Since no localised Alpha factors are available for regions outside of North Sea, these factors are conservatively applied everywhere in the world. In a region with benign weather characteristics such as the Mediterranean, this could be overly conservative for the selection of operational weather windows. A deterministic weather forecast is sufficient to assess weather risk for short term operations; nonetheless, uncertainties of longer term predicted weather should still need to be addressed. Shore float-in of umbilicals and cables requires a number of sequential activities with associated durations that build up to a total timeframe. This timeframe is beyond what can be accurately assessed using only deterministic weather forecasts. The operational activities are also very sensitive to tidal, current & sea-state variation; particularly associated with the use of personnel in the water like divers and waders for the removal of floats and the use of small crafts for control of the of the product alignment. The use of Ensemble Forecast which utilises probabilistic approach compared to the deterministic approach, addresses the uncertainty of long term weather forecasting and remove artificially added conservatism such as the Alpha factor. This forecast is derived from multiple simulations, each with minor variations of initial conditions and slightly modified weather models. Ensemble Forecast has been applied in offshore operation planning and execution in a project offshore Egypt in Mediterranean; particularly for a shore float-in of a main umbilical. It was used to define the main operational window, the start of the operation and weather risk beyond deterministic weather forecast. The use of the Ensemble Forecast for selection of overall weather window has been shown to optimise operability, reduce the risk of product being damaged, provide added confidence in the offshore operational safety for the personnel involved while minimising waiting on weather. The strategy of defining storm riding configuration for umbilical could enhanced overall operability. When the operational restrictions relating to limiting activities are anticipated to be surpassed but remains still within the storm riding sea-state, these activities could be safely halted and product held in place in stand-by mode until the weather conditions improved without affecting its integrity or overloading installation equipment.