TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractIn this paper, a Middle East field example is shown to illustrate the application of new advances in Logging While Drilling measurements. In addition to standard two mega-hertz multi-depth resistivity, neutron and gamma ray LWD measurements, azimuthal density and photoelectric factor (Pef) measurements were recorded. The real-time and recorded mode applications of azimuthal density and Pef are discussed in this paper.Conventional LWD density measurements are circumferentially averaged. This technique will smear the density output at bed boundaries, especially in horizontal wells where the bed's relative angle to the well bore is high. Information from azimuthally acquired quadrant density measurements can be used to clearly detect and evaluate bed boundaries in deviated and horizontal holes. In this paper, it is shown how up and bottom densities are used to accurately locate bed boundaries and other geological features such as faults. For geosteering purposes, up and bottom density displacement was able to show if the bed was being entered from the top or bottom of the well bore. It was also possible to estimate structural dip in real-time.Sixteen azimuthal density and sixteen azimuthal Pef sectors were recorded in downhole memory. Once these LWD data were retrieved from the BHA memory and image processing and image orientation was done, structural features such as fault, bed boundaries and formation heterogeneities were identified. True dip was computed from the density image. The compilation of this information allowed further evaluation of the geologic model of the carbonate gas-bearing reservoir.

In the past ten years, time-lapse (4D) seismic has evolved as a standard way of monitoring reservoir performance. The method is now being used as good reservoir management practice to provide evidence of saturation changes within the reservoir at field scale. 4D provides a new piece of data describing the dynamic behavior of the reservoir fluids between the wells, often limited to small scale monitoring at the borehole scale. Thus, it provides sophisticated techniques for reservoir monitoring and management relying on the integration of geological models, static and dynamic properties of the reservoir rock, and detailed production and pressure field data. While 4D seismic data has been very successful in monitoring hydrocarbon production from clastic reservoirs, this work has focused on implementing 4D time lapse to monitor saturation changes in carbonate reservoirs and it’s capability to be used as enhanced oil recovery (EOR) tool that can help in enhancing the recovery factor for the filed and help to locate new drilling to sweep more oil out of the reservoir and locate the by-pass oil. The principal goal of this research was to detect the maximum change in seismic attributes (amplitude, acoustic impedance, travel time) that could occur as a result of oil production, water and gas injection in carbonate reservoirs by using time-lapse 4D seismic.

A zero offset VSP survey was acquired over a thick carbonate interval. The objectives of the repeat survey were to assess repeatability of the measurement, robustness of the time lapse VSP processing mainly to account for time lapse noise and quantification of the time lapse signal in the reservoir due replacement of water by gas caused by gas injection that occurred between the baseline and repeat surveys. A long side of the two VSP’s, an array sonic (SDT) and the sonic scanner tools were run. The SDT was run to recover the monopole compresssional and shear waves, while sonic scanner to acquire both the dipole and monopole shear and compressional. Data processing was focused on isolating the time lapse signal in the reservoir section by comparing the baseline and repeat VSP surveys and sonic logs. Both the baseline and repeat surveys were processed with identical parameters to ensure that the datasets are comparable at every processing step. The processed data shows a good degree of repeatability, and deterministic deconvolution as expected was enough to take care of source wavelet variations between the two surveys. The time lapse VSP and sonic logs were run in carbonate reservoirs where gas is being injected to assess the effectiveness of recovering more oil as part of Enhanced Oil Recovery (EOR). The current recovery mechanism in the reservoirs is to inject water to enhance pressure support. The gas pilot objective is to increase the recovery factor to recover more oil and enhance productivity.

When implementing any field development plan or an Enhanced Oil Recovery (EOR) project, it is critical to understand the key variables that influence the success of the plan such as; reservoir parameters and fluid properties. Mature Oil & Gas fields' increasing complexity of recovery mechanisms dictates an improved understanding of the fields' behaviour and the technologies that must be applied to maintain and prolong oil production plateau and achieve ultimate recovery potential. History matching forms an integral part of the reservoir modeling workflow process. It is used to examine the field performance under different production and injection scenarios in order to select the best scenario for hydrocarbon production. However, the history-matching process can be very frustrating and time-consuming, even for fields that appear relatively small and simple in nature, because of the reservoir processes involved and the non-unique nature of the solution. Traditionally, history matching is conducted as a deterministic process with a single realization considered representative at a single point in time. Although, the input data usually go through a data analysis process where the major uncertainties and scenarios are defined, and uncertainty ranges are created, time and budget constraints usually result in significant reductions in the number of sensitivity runs and analysis for the input data validation and quality control that results in an incomplete investigation of the uncertainty quantification. Therefore, uncertainties inherited in the Petrophysical data are carried from the static model construction throughout the entire dynamic modelling process, ultimately leading to less-than-optimal models to be used as a decision making tool. Consequently, due to the non-uniqueness of the numerical solution, a good history-matched model might have geological and petrophysical properties quite far from those of the "Field" and therefore could lead to a bad forecast. As in any numerical model, petrophysical data quality is fundamental for model precision.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractWell bore images become increasingly important in identifying formation features and their possible extent. There are two different tools that acquire image data, acoustic and micro-resistivity. Both tools faced difficulties and challenges in acquiring quality data over the deviated and horizontal section of a well.To perform quality image data in deviated and horizontal section of a well is difficult because of; firstly, drilling rogues, deviated and horizontal section, and these results in poor padwall contacts. Therefore, the quality of the resistivity image data is highly affected by the drilling fluid, along with the acoustic data. Secondly, poor mud properties that behaves as a blocking medium to acquire quality data.A new technique requires modifying in both drilling and mud properties has been applied in different fields with high success. This new technique requires certain bottom hole assembly and drilling parameters, along with drilling fluid properties to better drill smooth holes.The new technique resulted in smooth horizontal section and better in the deviated section, therefore, better pad-wall contact. Images from both; resitivity and acoustic modes provided high quality data acquisition. As a result, geological features were very clear by the image logs after the implementation of this new technique.In this paper, the new technique is explained along with case histories from three different fields of the image logs are presented and compared to previous poor quality logs.