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The objective of this study is to analyze the performance of non-conventional wells drilled in Hassi-Messaoud field, Algeria. A new technique "Direct Synthesis" developed by Dr. D. Tiab1,2 is used for the pressure transient analysis. It permits the determination of permeability tensor as well as the effective length of the horizontal well. Hence, and for the first time, the permeability tensor (Kx, Ky, Kz), and the vertical permeability anisotropy (Kv/Kh) were obtained. The results of the interpretations lead to a verity of information and correlations. Sensitivity studies allow the optimization of future horizontal drilling plannings. The comparison between the performances of slanted, horizontal, and multilateral wells shows that slanted wells, regarding the low risk, are the most appropriate for Hassi-Messaoud field. From the spatial distribution of permeabilities, Kx, Ky, Kz, important conclusions are illustrated regarding the geological model of the field. Horizontal wells are not only beneficial for improving productivity but also for the tremendous amount of information they provide. Form this study several recommendations are issued regarding the well spacing taking into account different geological models. Introduction Hassi-Messaoud field has four (04) reservoirs (R3, R2, Ra, and Ri). The Ra is the principal reservoir within 100m of average thickness; it is subdivided in five (05) layers or drains (D1, ID, D2, D3 and D4). The cutout of Ra is made in many zones that are limitted by the sectors of low characteristics. Historically, the produced hydrocarbons during the last four decades represent less than the half of mobile hydrocarbon in place. To reach the best recovery in Hassi-Messaoud oil field, two points should be realized:Perfect knowledge of reservoir architucture, andOptimal reservoir management and development. For the efficient investigation of petrophysical parameters and their spatial distribution, The reservoir is characterized by newly geostatistical methods. As a result, the structure of four units (R2, Lower Thick Level (LTL), D3-D4 and Riso) and the organization of petrophysical parameters in bands of high to average permeabilities, oriented in North-Est/South-West direction, are established. However, the development of sectors of low petrophysical chracteristics is conceivable only by the use of non-conventional techniques such as horizontal and deviated wells or by modifying oldest vertical wells to short or medium radii. It is important to summon up that previously in Hassi-Messaoud field, the scope of anisotropy (kv/kh) and the permeability tensor in space (kx, ky, kz) have never been measured. However, the present synthesis, based on field results of transient pressure response analysis performed on non-conventional wells, is well investigated for vertical and horizontal anisotropies evaluation. Analyses and Results In this work, the first step consists on analyzing pressure response by the following computer softwares, Saphir, Interpret II, and Welltest-PED using non-linear regressions as well as specialized plots. Knowing that these softwares present many limitations such as:Restrictive hypotheses in analytical methods.No means for result control, andShortage in output parameters for reservoir characterization in their globality.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractInformation obtained from testing horizontal wells is very useful in reservoir characterization, in this paper the experience of horizontal wells in the gas reservoir of TIN FOUYE TABANKORT (TFT), Algeria is illustrated, as well as the contribution in characterizing natural fractures.The transient response (Build Up) of two horizontal wells were simulated, the two short radii TFT#z329 (400m), and TFTz#333 (200m) were drilled in the same azimuth the numerical match yields to the following permeability tensors: well TFTz#329 (Kx = 2 md, Ky = 90 md, and Kz = 110md), and well TFTz#333 (Kx = 5 md, Ky = 100 md, and Kz = 115 md).The permeability tensors obtained correspond to a configuration indicating a plan of oriented fractures. The wells have been drilled perpendicular to the fractures. The matrix permeability is K matrix = 5 md and the fractures permeability K fissures = 100 md . these results were confirmed by the imagery (FMI, ARI) run in both wells. Laboratory tests on cores of vertical wells confirmed these results and gave the fractures permeability K fractures = 70 md.

The economical viability of the Cambrian sandstone reservoirs in the Hassi Messaoud field is closely linked to the presence of fractures. Natural or hydraulically induced fractures control hydrocarbon productivity due to the low porosity, low matrix permeability and heterogeneous sedimentological characteristics of these fluvial deposits. Fracture corridors and permeable fault zones also represent a major risk of water breakthrough from the underlying aquifer in horizontal wells. The identification and characterization of open fractures and conductive faults is of critical importance for the completion decisions in this field. Whole cores enable a comprehensive description of fractures (morphology and type) over the cored sections of the reservoir. Meso-scale fractures can also be identified, oriented and characterized (open vs. cemented) on high resolution borehole images over the entire open-hole section. When combined with pressure transient analyses and production data, borehole image logs provide invaluable information on the enhanced fracture conductivity, the completion optimization and the reservoir management for sustaining long term production in these complex reservoirs. Wells with high fracture density usually correlate with high production rates as long as the dominant fracture strike is close to the direction of the maximum in-situ horizontal stress (sH). Wells with low fracture density or dominant fracture strike oriented oblique or perpendicular to sH generally show poor production rates. This paper discusses case studies of fracture and fault characterization from a combination of borehole images with production and pressure transient data to provide an explanation for ambiguous production observations and well test data. Examples of completion optimization utilizing this integrated approach are also presented. 1. Introduction Although it is widely admitted that the presence of fractures (natural and hydraulic) is directly linked to the production of the hydrocarbon trapped in the Cambrian reservoirs of the Hassi Messaoud field, very little is known about the relationship between their properties and spatial distribution with the dynamic measurements of the reservoir. Extensive core analyses have shown that permeability anisotropy at different scales is controlled by the interplay of depositional facies and fracture systems in this field. The design, execution and economic aspects of hydraulic fracturing to improve well productivity by limiting the effect of permeability anisotropy in the Cambrian reservoirs of Hassi Messaoud field have been studied by many authors. These topics are particularly well documented by Rahmouni et al, (2002) and Guehria et al, (2005). Similar patterns in production profiles, with high initial production rates followed by a sharp decline, have been observed across the majority of both hydraulically fractured and conventional wells in Hassi Messaoud field. In the majority of the transient test data performed in horizontal wells, the analysis of the pressure derivative reveals that production comes from both natural fractures and layered media in a bilinear flow characterized by a slope of ¼ (m = 0.25) of the Log-Log pressure-derivative plot (Azzouguen et al, 2000).