Sandface completions such as standalone screen completions have suffered from erosion problems for many years. A significant amount of catastrophic screen failures are considered to be the result of high velocities of solid's laden hydrocarbons creating hot spot areas in the interface between the sandface and the completion. Previous researchers investigated the change in permeability of failed rock into annular gaps generated in non-compliant sand control completions and identified that packed material in this space can result in severe distortion to flow patterns and restrictions. This paper describes the development and testing process for a new methodology that allows identification of the erosion prone areas in the annular space between the sandface and the screen. Detailed investigation, supported by laboratory testing, reviewed oil and gas well conditions at the startup, during a cleanout and after hydrocarbon's production have been stabilised. Radial flow, mode of sand collapse, compaction, voidage, sand quality and formation petro-physical properties were tested and analysed using high and low pressure flow cells in order to quantify the changes in pressure drops through the collapsed rock material. The results indicated that flow rate, viscosity, voidage, grain shape and volume are the main contributors to the variations in pressure drops across failed sand material in the annular space. On the basis of these tests, a continuous (foot-by-foot) analytical model was developed that allows identification of the specific location and variation in pressure drops across the annular packed material for oil and gas wells. The model is composed of five (5) main elements; a reservoir inflow module, a fluid drag module, a grain size and volume module, a pressure drop module and an erosion prediction module. The model was tested using data from a North Sea field and the results, algorithms and field samples will be discussed and presented in detail.

In water injection programs it is accepted that the temperature at which water arrives at the formation will cause the rock to shrink resulting in a reduction in the minimum horizontal stress and possibly a fracture of the rock. This effect is known as TIF or Thermally Induced Fracturing. However, little research has been carried out as to how the cooling of the rock by the injection water affect the formation mechanical properties. This paper presents work carried out to determine the effect of temperature changes on the strength of sandstone reservoirs used for water injection.An effort was initiated by Pluspetrol Norte, S.A. as part of their produced water disposal programs to develop an understanding as to how various sandstone reservoirs used for re-injection respond to temperature changes and what implications can it have for their operations. Pluspetrol production comes from two(2) main blocks in Northern Peru, Total water production has reached over 1000000 bwpd of which over 450000 bwpd are currently being re-injected throughout both blocks.A large core testing program was designed and completed to measure unconfined rock strength in a number of sandstone cores available from both blocks. The cores were heated and cooled and their strength measured to identify possible changes in strength magnitude. The results obtained were analysed and compared with those available in a large geomechanical model of the blocks developed earlier known as the Custodian (1) , a new predictive model was developed using the results obtained. A number of simulations were carried out using a TIF model to compare the measured field data during water re-injection with the predictions from the TIF model using the new strength model. These results are presented in detail and its application to other geomechanical problems such as sand production in water injectors is also discussed.

TX 75083-3836 U.S.A., fax 01-972-952-9435. AbstractSand production is a serious historical production problem in the Forest, Cruse and Nariva reservoirs of the Gulf of Paria offshore Trinidad. Venture Production Trinidad drilled, completed and tested 10 wells in 2002. Sand production has been no more than a trace in all but one of the tests so far. Sand control has been undertaken without recourse to the traditional mechanical methods of sand screens and gravel packs. A carefully planned approach integrating modern methods of well-bore stress analysis and sand production prediction from log interpretation has delivered this result. A well-bore stress study reviewed all available data from the Brighton Field, including old drilling reports and logs. The study has been updated with modern data from the 2002 drilling programme. A well-bore stress model was developed. A sand prediction study delivered an understanding of the mechanics of sand production in the area which was fed into the well-planning process. Well data and logging data were analysed with very short turnaround times to deliver a sand production prediction log. Perforated intervals were selected using the log to avoid intervals with a high probability of sand production. Perforating techniques were also selected to minimise the likelihood of sand production without compromising productivity.

In non-compliant sand control completions such as stand-alone-screens, the annular gap between the wellbore wall and the screen has always been considered detrimental to efficient inflow. They are typically associated with large skins resulting from the mixing of failed sand grains and the development of a new and continuously changing permeability as the collapsing material starts to compact onto the screen. Annular movement of sand grains and non-uniform bridging creating "hot" spots will eventually lead to erosion and completion failure. Previous researchers have investigated the change in permeability of failed rock into annular gaps generated in non-compliant sand control completions and identified that packed material in this space can result in severe distortion to flow patterns and restrictions. This paper describes the mechanical and flow process occurring as the wellbore wall collapses onto the screen surface. Constitutive models are used to characterise the mechanical behaviour of the failed material in terms of deformation and collapse of the near wellbore onto the screen. Continuous (foot-by-foot) inflow models are presented to illustrate the impact of the deformation process as the annular gap is filled up on inflow. A detailed laboratory testing program and its results are presented to validate both processes using samples from North Sea sandstone reservoirs. The results indicate that for noncompliant sandface completions such as stand-alone screens, it is possible to determine whether the collapse of the wellbore will occur and how productivity will be affected. From the mechanical point of view the rock follows an extension-dilatancycompaction path. This will at the same time produce a varying permeability and hence inflow, the magnitude of which will depend on factors such as pore pressure, drawdown pressures, reservoir rock mechanical properties and mineral composition. This extensive testing program has led to the development of a series of analytical models, testing procedures and design methodologies for wells being completed with non-compliant sand control completions.

Sand control operations and particularly those using granular filter media such as gravel packs and frac & pack are being carried out in increasing numbers and in more demanding environments. Improvements continue to be made in terms of equipment, fluids and operations. However, with the increasing emphasis on well productivity and minimizing impairment, it is clear that a better understanding of some of the current causes of impairment is required.The design of sand control filter media continues to be based on a limited number of discrete formation samples that are taken to be fully representative of the actual grain sizes throughout the interval of interest. It is often difficult to clearly identify the causes and location of the impairment unless expensive evaluation tools such as PLTs are utilized. This paper presents the results of research work that have successfully resulted in an analytical tool and a new granular system that allows improved design and evaluation of sand control operations. A system for the determination of grain size and pore blocking mechanisms on a foot-by-foot basis has been developed. Furthermore a granular filter media has been devised such that permeability damage from solids migration can be reversed. The results presented are based on "flow of solid particles through porous media" principles. The work included laboratory t esting for various gravels and these results are also included. Field validation was carried out with data from LDAs and an offshore deviated well.