New Applications Of Proven Sand Technology In High-Angle Holes
Authors: Walling Richard , Stabler Frank , Baxter Charles 
Published: December 2007

Gravel pack technology can be effectively used in high-angle completions, as evidenced by applications in the High Island area, offshore Texas. A combination of factors led to this success. Though careful in-depth planning was essential, on-site, technical expertise during implementation was vital to success.

Economics demanded a new application of proven sand control technology, incorporating a precise selection of beads, packing aggregate, screen type, perforating guns, and gravel pack process.

Viscous slurry packing made installation possible in high-angle holes and long, perforated intervals without loss of productivity. High rate pressure packing can create costly pack contamination or result in premature bridging.

In perforating operations, both bullet and jet methods were used; jet perforating employed late in the project performed equally well and caused fewer problems. In the long intervals, perforation washing proved to be a better means of perforation clean-up.

After the gravel packs were installed, the wells were tested to establish the integrity of the completions. Production rates up to 11.2 MMcfd were achieved with no sand production.

GENERAL CONDITIONS

The High Island area, offshore Texas, is characterized by producing intervals in shallow Pleistocene formations. After exploratory holes determined the profitability of the area, platform development was decided on as the most effective method. However, the producing formation's shallowness and faulted nature required high-angle (60 deg. +) holes.

A full site of logs was run on each well. In addition to the routine information concerning interval length, lithology, porosity and permeability, an indication of rock strength was obtained through a computed formation properties log. This log used the shear modulus and bulk modulus to develop a sand-production coefficient.

Each of these High Island formations had coefficients indicating they were highly rate sensitive. Two drill-stem tests substantiated this prediction. Significant amounts of sand were produced at low flow rates. As the flow rates were accelerated, sand production increased (in one case, sanding up the drill string).

Evaluation of full hole cores extracted from pay zones showed low compressive strength and an unconsolidated nature; log analysis of pay zones from each wellbore indicated long (300 ft. +) sand members separated by shale breaks (Fig. 1). These factors dictated the need for a proven sand control method - gravel packing.

GRAVEL PACK DESIGN

Existing gravel packing design criteria were reviewed. The five basic properties isolated for selection were gravel size, packing material, screen type, gravelpack process, and perforating apparatus.

Gravel Size

First, the specific size range of the packing material was denned. From full-hole rubber sleeve cores, sieve analyses were run to determine the formation sand-size distribution. This information was then compared with sieves taken from side wall cores extracted from potential drainage points. By this comparison, the validity of the side wall cores could then be verified as a useful design point.

After determining the validity of the formation sand-size distribution from the side wall sieves, the specific size range of the packing material could then be defined. In doing this, all the side wall core sieves from a given production interval were compared. The least coarse of these samples was taken and used to determine the correct packing aggregate (Fig. 2).

After reviewing literature on aggregate sizing, a combination of methods was concluded to be the most advantageous.