ABSTRACT:Deploying an autonomous unmanned aerial vehicle in GPS-denied areas is a highly discussed problem in the scientific community. There are several approaches being developed, but the main strategies yet considered are computer vision based navigation systems. This work presents a new real-time computer-vision position estimator for UAV navigation. The estimator uses images captured during flight to recognize specific, well-known, landmarks in order to estimate the latitude and longitude of the aircraft. The method was tested in a simulated environment, using a dataset of real aerial images obtained in previous flights, with synchronized images, GPS and IMU data. The estimated position in each landmark recognition was compatible with the GPS data, stating that the developed method can be used as an alternative navigation system.

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The present work describes aspects related to planning and execution of six multilateral horizontal branches drilled underbalanced (UB) in Carmopolis field, which is located in Sergipe/Alagoas basin, in Brazil's Northeast Region. This field, discovered in 1963, is the country's largest onshore oil accumulation and has its production zones, which consist basically of sandstones and conglomerates, depleted at about 700 m deep (TVD). As the targeted formations are consolidated, UB drilling did not bring any special concern in terms of wellbore collapse. In order to achieve the required bottomhole pressure nitrogen was mixed with a synthetic based mud (SBM) after flowing down through the annular space between the 9 5/8" and 7" casings and passing through a 1" aperture in the 7" casing. After that, the two-phase mixture went up through the annulus between the 7" casing and the jointed pipe drill string. This concentric casing approach for injecting gas made possible the use of conventional MWD, but it brought some concerns, which are addressed and discussed, about the maintenance of the UB condition while operating. The first multilateral well UB drilled in Brazil is an example of the combination of different technologies as multilateral level 2 well design, UB condition and medium radius directional system. In addition, it also involved four different parties where the operating company worked together with two service companies and a drilling contractor to build a team and achieve operational success. Introduction Carmopolis field, which is located in onshore Sergipe/Alagoas basin, in Brazil's Northeast Region (see Fig. 1), is the country's largest onshore oil accumulation at 268 MMm3 OOIP and a current total oil production at about 2,880 m3/d. Discovered in 1963 and promptly brought into primary production, it mainly produces from the sandstone and conglomerate reservoirs of the Carmópolis/Muribeca formation and secondarily from the deeper Barra de Itiuba formation and the fractured methamorfic basement. The Carmopolis/Muribeca formation, which is composed of syntetonic conglomerates and fine clastic sediments, contains four major oil bearing zones, named CPS-1, CPS-2, CPS-3 and CPS-4. As a result, oil quality varies considerably throughout the stratigraphic column, but general reservoir data is given in Table 11. Waterflooding was first implemented in the southern part of the field in 1968. However, after three years of this pioneering implementation, the results were considered inconclusive and the project was abandoned. The combination of adverse fluid mobility ratio, reservoir heterogeneity, and the lack of proper selective injection led to the quick decline of production. Despite those uncertainties, waterflooding was resumed at the main block of the field in 1971 for attempting to revert a 30% production decline. Besides waterflooding, several other technologies have been implemented, as pilot projects, for improving oil recovery. Polymer flooding, steam injection and in-situ combustion have been introduced, tested and evaluated through the years. In summary, the Carmopolis field has been a kind of field laboratory for investigating a wide range of improved oil recovery (IOR) methods. For further details, a comprehensive history of the IOR applications in Carmopolis and the respective results is available in literature1.

The purpose of this paper is to review the planning, execution and results of a Seven Leg, Semi-short Radius Multilateral Well drilled underbalanced in a very mature field in Northeast Brazil. It will explain such details as ... why multilateral?? ... why semi-short radius?? ... why underbalanced?? ... in an effort to explain the many thought processes and considerations when designing and planning drilling operations in depleted reservoirs. Introduction The Carmopolis Field is located approximately 60km northeast of the city of Aracaju, in the State of Sergipe, Brazil. It is a very mature field that covers an area of approximately 140 square kilometers, and was discovered in 1963. The field has multiple pay zones with a total of approximately 350 million m3 of oil in place. To date, approximately 62 million m3 of oil has been produced and the field currently produces about 3000 m3/day of oil and 18000 m3/day of water. The field has gone through various phases of production enhancement scenarios over the past 20 years. Enhanced recovery methods such as water flood and steam injection have been implemented in various parts of the field. New techniques and technologies continue to be used in this field in an effort to enhance production and reservoir recovery even further. The combination of underbalanced drilling and ML technology is just one more step in the evolution of this field. Reservoir Description The Carmopolis reservoir is composed of syntectonic conglomerates and associated finer clastic sediments deposited in an alluvial-fan complex within fault bounded grabens(1). There are four major lithofacies which are part of the Cretaceous period. Each of these lithofacies can be distinguished on the basis of grain size, which decreases progressively in the direction of the sediment movement. The larger grained lithofacies have lower porosity and higher bulk density which allows identification of each lithofacie based on bulk density and gamma ray logs. Porosity and permeability relationships for each of the major lithofacies were obtained from core samples. Analysis has shown that both the porosity and permeability decrease in the coarser grained lithofacies, thus resulting in poorer reservoir quality. Project Goals and Objectives As in any new drilling project, the main objective is always to maximize return on investment. In a field that already has well over 1450 wells drilled in it, on 4 hectare spacings, finding a suitable location can be a challenge. The combination of low permeability (50mD - 1000mD) of the producing formations, and relatively heavy grade (20 - 21 API gravity) of the oil in place, severely limit the production rate from the vertical wells. Couple these two characteristics with the complex geology and faulting characteristics of the field. The combination makes finding economically viable drilling locations even more difficult. As vertical wells were no longer economic in many parts of the field, horizontal wells were the logical next step. A single high angle well was drilled through the CPS-1, CPS-2 and CPS-3 formations (300 m was drilled through the pay zones from top to bottom) for about 1.5 times the cost of a vertical well. After the high angle well was drilled, another location was identified and targeted for drilling. This location was selected as a favorable target because there was trapped oil discovered on a structural high between two faults. However, due to faulting in the immediate area, one long horizontal well could not be drilled and still get the desired reservoir exposure in all the producing zones. In addition only a couple of the zones would actually be produced, so a long well was not the best option. The location could also have been drained with three vertical wells, but in order to drain very near the fault, additional risk would have had to be taken, in case the well actually was drilled on the wrong side of the fault.

The present work describes not only the main aspects related to planning and executing six multilateral (ML) horizontal branches drilled underbalanced (UB) in Carmópolis field, but also presents an analysis of the initial productive life of this well. All the main engineering information used for making decisions while planning and at well site, drilling performance and production evaluation are included. As the targeted formations are consolidated, UBD did not bring any special concern in terms of wellbore collapse. In order to achieve the required bottomhole pressure, nitrogen was mixed with a synthetic base mud (SBM) after flowing down through the annular space between the 9 5/8" and 7" casings and passing through a 1" aperture in the 7" casing. After that, the mixture went up through the annulus between the 7" casing and the drill string. This concentric casing approach for injecting gas made possible the use of conventional MWD, but it brought some concerns about the maintenance of the UB condition while operating. The first ML well UB drilled in Brazil successfully combined the following different technologies:ML level 2;UB condition, andmedium radius build-up drilling system. It also involved four different parties where the operating company worked together with three service companies to build a team and achieve operational goals. As the reservoir pressure was not sufficient to sustain the flow of oil to the surface, this paper also addresses the design of the pilot well, which was specifically prepared for operating with a sucker rod pump (SRP). Finally, from the perspective of the reservoir engineers in charge of developing this field, the oil production is presented and evaluated. Introduction Carmópolis field, which is located in onshore Sergipe/Alagoas basin, in Brazil's Northeast Region (see Fig. 1), is the country's largest onshore oil accumulation at 268 MMm3 OOIP1. Up to now, approximately 62 million m3 of oil has been produced and the current total oil production runs at about 2,880 m3/d. Discovered in 1963 and promptly brought into primary production, it mainly produces from the sandstone and conglomerate reservoirs of the Carmópolis/Muribeca formation and secondarily from the deeper Barra de Itiuba formation and the fractured methamorfic basement. The Carmópolis/Muribeca formation, which is composed of syntetonic conglomerates and associated fine clastic sediments deposited in an alluvial-fan complex within fault bounded grabens, contains four major lithofacies that can be distinguished on the basis of grain size2. Those oil zones, named CPS-1, CPS-2, CPS-3 and CPS-4, are part of the Cretaceous period and decrease progressively in the direction of the sediment movement. The larger grained lithofacies have lower porosity and higher bulk density, which allows identification of each lithofacie, based on bulk density and gamma ray logs. Analysis has shown that both the porosity and permeability decrease in the coarser grained lithofacies, thus resulting in poorer reservoir quality. As a result, oil quality varies considerably throughout the stratigraphic column, but general reservoir data is given in Table 11. Waterflooding was first implemented in the southern part of the field in 1968. However, after three years of this pioneering implementation, the results were considered inconclusive and the project was abandoned. The combination of adverse fluid mobility ratio, reservoir heterogeneity, and the lack of proper selective injection led to the quick decline of production. Despite those uncertainties, waterflooding was resumed at the main block of the field in 1971 for attempting to revert a 30% production decline. Besides waterflooding, several other technologies have been implemented, as pilot projects, for improving oil recovery. Polymer flooding, steam injection and in-situ combustion have been introduced, tested and evaluated through the years. In summary, the Carmópolis field has been a kind of field laboratory for investigating a wide range of improved oil recovery (IOR) methods. For further details, a comprehensive history of the IOR applications in Carmópolis and the respective results is available in literature1.