International Petroleum Conference and Exhibition of Mexico

The oil outflow from porous-rock blocks due to water imbibition interchange and to gravitational drainage, are described by schematic mathematical models that include actual petrophysical properties of the fluids as well as dimensions of the blocks. The models were validated through comparison of their results with those of numerical simulations of these problems. The simulations cover wide realistic ranges of values of the properties involved.

The models can be used to compute the expected behavior of blocks in fractured reservoirs and to calibrate block behavior in numerical simulators that use parameters instead of actual properties of the fractured porous media.

P. 71

Abstract

Simulation of multiphase flow in porous media requires knowledge of relative permeability functions. A commonly used unsteady-state method of estimating relative permeability is based on interpreting flow data collected from laboratory displacement experiments. In this paper, refinements are outlined, for improving the accuracy of estimated relative permeability pararmeters by accounting for thermal effects for produced fluids, utilizing pre breakthrough differential pressure data in cases where capillary forces are neglected, elimination of convergence problems in history-matching algorithms, and improving the reliability of injected phase relative permeability estimates.

For the gravimetric method of collecting displacement data, the existing procedure of calculating production volumes is improved to account for thermal expansion of fluids in collection vessels, both for imbibition and drainage displacement. The parameter estimation technique is used to determine relative permeability. A semi-analytical procedure, based on the JBN method, utilizes pre-breakthrough differential pressure data, in cases when capillary forces are neglected. This is especially important for low permeability samples, where post-breakthrough production data could be limited. Otherwise, capillary and gravitational forces are accounted for using a finite- difference method.

The history matching procedure requires minimizing the objective function, which is a measure of the deviation between simulated and experimental data. The simulated annealing method is used to avoid possible convergence of the minimization routine to a local, rather than the global minimum of the objective function. Interpretation of relative permeability of the injected fluid from displacement experiments is shown to be less precise than for the displaced fluid. The theoretical analysis rationalizes acquisition of more data during early phases of a displacement experiment. Optimization features discussed in this paper are incorporated in a new, relative permeability simulator.

P. 77

Abstract

High-temperature fracturing-fluid breaker systems have been used in fracturing operations for the past several years. The advantage of using these systems has been improved fracture conductivity, but there has been an increased risk of poor proppant placement and premature screenouts resulting from early viscosity reductions as the fluid is exposed to high temperatures. In many cases, this problem could only be avoided by adding breaker to the final portion of the proppant stages, essentially improving the fracture conductivity in the nearwellbore region without enhancing the conductivity of most of the proppant pack.

This paper highlights innovative research for developing high-temperature breakers that work synergistically with gel stabilizers to maintain excellent gel viscosity. This viscosity allows sufficient time to place the treatment while still providing a more complete break and improved fracture conductivity. Laboratory testing has shown that this high-temperature breaker system can be used effectively at temperatures as high as 350 F without sacrificing early-time fluid viscosity or proppant placement, while still providing dramatic improvements in fracture conductivity.

Field production has been analyzed and shows the combined benefits of improved proppant placement and increased fracture conductivities obtained with the application of this technology.

P. 409

Ansai field is a typical field with low permeability, low pressure, low production and the water flooding is inefficient. In order to explore an effective developing method for increasing the production and ultimate recovery, we carried out the feasibility studies of natural gas flooding. This paper analyses the feasibility of natural gas flooding from the geological condition of Ansai field at first, then introduces the high pressure slim tube tests for determining MMP of injection gas and reservoir oil and prediction of MMP with published correlation. The high precision correlation has been selected for predicting the composition of injection gas in miscible displacement. The performance of natural gas flooding have been simulated using MVIP simulator. The results shows that Ansai field shares the geologic conditions for natural gas flooding. The MMP of lean gas and Ansai reservoir oil is above 32MPa, and the average reservoir pressure is only 8.81 MPa in Ansai field, so the lean gas flooding is immiscible displacement at Ansai reservoir condition. If accomplishing a miscible displacement at the same condition, the composition of injected gas must be changed by increasing rich gas content, the content is 80%C2H6 . The results of numerical computations shows that the recovery ratio of natural gas flooding (26.3%OOIP) is more than of water flooding (20.6%OOIP).Obviously, the natural gas flooding is a hopeful EOR method in Ansai field. These studies provides scientific evidence for the policy of natural gas flooding in Ansai field.

P. 371

Abstract

Pulsed neutron capture logs have long provided a means of determining water saturation and estimating porosity of formations behind casing. Recent technological advances in pulsed neutron logging have resulted not only in improvements in saturation and porosity data, but also in the capability to provide information regarding water entry and flow, lithology, and improved differentiation of gas-filled zones from tight formations. These advances provide greater accuracy in reservoir evaluation and monitoring as well as improved completion and production diagnostics.

Inelastic, capture, borehole, and background spectra are now utilized to enhance porosity estimates, identify water flow, and help determine lithology. Modular tool design allows the pulsed neutron tool to be combined with production logging tools for more reliable production diagnostics. Simple tool modifications permit quantitative measurements of water velocity and borehole oil holdup. The modular design also allows additional detectors to be placed in the toolstring for lithology identification and gravel pack evaluation.

This paper discusses this new pulsed neutron capture technology and gives an overview of the expanded range of pulsed neutron applications. Field examples of waterflow detection, gravel pack evaluation, oil/gas discrimination, and conventional analysis are presented from offshore wells in the Gulf of Mexico and from onshore wells in Mexico and the U.S.

P. 287

The equations describing the transient flow of a fluid with low compresibility through a series of connected porous media with contrasting geometries and/or properties were coupled into one single vector equation. That equation describes pressure and flow velocity at any point in that composite medium and in the Laplace domain. Numerical symmetric transforms are used to obtain solutions in terms of time.

A distinction is made between actual composite geometries in which flow is delimited by actual boundaries in different configurations; and virtual composite geometries, in which flow geometries are observed in pressure plots though no physical boundaries guide the flow.

The formulation was validated through applications to cases presenting composite geometry flow patterns that have been analyzed previously through approaches different from the one presented.

P. 9

Abstract

Brown & Root's BARBOX concept is an alternative, purpose-built, deep-draft monohull system for floating production, storage, and offloading (FPSO). This FPSO system concept has been designed for worldwide applications including West Africa, the North Sea and the Gulf of Mexico environments. The BARBOX's stiffened flat plate construction gives it a low capital investment cost compared to systems with minimum water plane hull types (e.g.. semi-submersible, SPAR, TLP) and ship-shaped FPSO. The BARBOX's dynamic motion characteristics are similar or better than those of comparable ship-shaped FPSO configurations. This paper also considers construction of the BARBOX hull in the Gulf of Mexico region. A recent Brown & Root study indicated that the Gulf coast fabrication yards were technically capable to fabricate the BARBOX hull and they could be cost competitive against worldwide shipyards.

P. 249

Abstract

Pol-A compression platform belongs to a petroleum platform complex located in the Pemex Exploracion y Produccion's marine zone in the Gulf of Mexico. It receives the natural gas, that is first separated from oil in the production platforms, via two pipelines called high pressure suction and low pressure suction. The natural gas once on the compression platform is conditioned, compressed and sent to Atasta, an onshore recompression station. It Also produces sweet gas to supply fuel gas for all the equipment and machines located on the platform complex.

Pol-A compression platform handles 320 MCF (million cubic feet) of natural gas per day and 30 MCF of fuel gas per day. Its operation in the marine zone began in 1988 and it belongs to a high gas producer oil field.

P. 103

Abstract

The modem reservoir management process involves establishing a purpose or strategy and developing a plan, implementing and monitoring the plan, and evaluating the results. This paper present application of them on Pantai Pakam Timur gas field.

Pantai Pakam Timur is a new gas field in Pertamina Operasi Rantau Aset Pangkalansusu. This field located in the onshore portion of the North Sumatra Basin Indonesia. The Area is approximately 15 km North-West of Medan. The Pantai Pakam Timur Structure was discovered as gas and condensate entrapment in the major of Belumai formation (Z-238S,2400), Apart from that, there is Shallow prospect of Keutapang formation (Z-l27S) is known brightly as "Strong reflection" in Seismic which about 1300 milli Sec.

Since the test production has just started about 9 years ago, it is very important evaluate the reservoir characteristics to obtain reliable data to set up the future field development strategy. The Pressure Transient testing of several wells show existing very difference of rock characteristic (the main is permeability) between deep zone (Z-238S,2400) and shallow zone (Z-l27S), which on deep zone less than 5 Md, then on shallow zone (under discussion) the fantastic permeability had been found, they were greater than 500 MD from PPT-05A and PPT-06 wells.

The monitoring and evaluating are being performed through several technical approaches respectively, which are continuous monitoring on production performance, evaluating on well testing analysis and evaluating the P/Z versus Cumulative gas production plot, that is used by comparing toward Volumetric method, in line to Reserve estimation.

Furthermore the gas deliverability was conducted based on modified isochronal test results of several existing wells and appropriate Reserve to get more realistic and maximize the potential. (The strategy and developing stage).

P. 127

Designing gas injection projects in naturally fractured reservoirs requiresspecial considerations which, in turn, relies on knowledge of the fracturenetwork. Characterization of the fracture network involves delineation ofimportant physical characteristics, such as fracture spacing, fractureorientation, fracture conductivity (of both natural and hydraulically inducedfractures). Of equal significance is understanding the transfer mechanismsbetween oil and gas in the rock matrix and injected water and gas present inthe fracture network.

Integration of fracture characterization with results obtained duringexperimental investigation of transfer mechanisms is a key step for historymatching and predicting reservoir response to water or gas injection. Thispaper describes the steps taken in two important areas of 1) fracturecharacterization and 2) fluid exchange from fracture to matrix as a precursorfor design of a 10 acre CO2 pilot in the naturally fractured Spraberry TrendArea.

Fracture and matrix characterization are based on oriented vertical andhorizontal core taken from Upper Spraberry reservoirs. Fluid exchangemechanisms are investigated in reservoir plugs and whole core at reservoirtemperatures and pressures. Results of imbibition/wettability and CO2 gravitydrainage experiments are presented. History matching Spraberry waterfloodperformance and predicting performance. under CO2 injection is presented basedon integration of reservoir characterization and laboratoryexperimentation.

P. 325